ở người tính trạng mắt nâu A, mắt đen a, tóc xoăn B, tóc thẳng b
a. bố mắt nâu tóc xoăn và mẹ mắt đen tóc thẳng con của họ có KG,KH ntn ?

b. nếu bố mẹ đều có mắt nâu tóc xoăn sinh được 4 đứa con, đứa đầu mắt nâu, tóc thẳng, đứa thứ 2 mắt đen, tóc xoăn, đứa thứ 3 mắt nâu, tóc xoăn, đứa thứ 4 mắt đen, tóc thẳng. Tìm KG bố mẹ và các con

ở lúa cây cao A là trội so với cây thấp a, chín sớm (S) chín muộn (s) 2 cặp gen này tồn tại trên 2 NST thường

a. viết kiểu gen có thể có cây cao chín muộn , cây thấy chín sớm, cây cao chín sớm
b. đem lai lúa cây cao chín sớm với cây thấp chín muộn thu được F1: 204 cây cao chín sớm, 201 cây cao chín muộn,203 cây thấp chín sớm , 200 cây thấp chín muộn. biện luận để tìm kiểu gen cây bố mẹ và viết sơ đồ lai

Tính giá trị của biểu thức:

a)  x − 5 . x + 12 với x = 7

b)  − 55 . − 25 . − x với x = 8

c)  − 1 . − 2 . − 3 . − 4 − 5 . x với x = 10

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 43 to 50.

     It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species' death vary from situation to situation. Rapid ecological change may render an environment hostile to a species. For example, temperatures may change and a species may not be adapted. Food resources may be affected by environmental changes, which will then cause problems for a species requiring these resources. Other species may become better adapted to an environment, resulting in competition and, ultimately, in the death of a species.

     The fossil record reveals that extinction has occurred throughout the history of Earth. Recent analyses have also revealed that on some occasions many species became extinct at the same time - a mass extinction. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life. Perhaps the largest mass extinction was the one that occurred 225 million years ago, when approximately 95 percent of all species died. Mass extinctions can be caused by a relatively rapid change in the environment and can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, even affect organisms not living in the oceans. Such a change would probably lead to a mass extinction.

     One interesting, and controversial, finding is that extinctions during the past 250 million years have tended to be more intense every 26 million years. The periodic extinction might be due to intersection of the earth's orbit with a cloud of comets, but this theory is purely speculative. Some researchers have also speculated that extinction may often be random. That is, certain species may be eliminated and others may survive for no particular reason. A species' survival may have nothing to do with its ability or inability to adapt. If so, some of revolutionary history may reflect a sequence of essentially random events.

In paragraph 3, the author makes which of the following statements about a species' survival?

A. it may depend on chance events

B. it does not vary greatly from species to species

C. it reflects the interrelationship of many species

D. it is associated with astronomical conditions

Read the following pasage and mark the letter A. B, C or D on your answer sheet to indicate the correct answer to each of the questions from 41 to 48.

Another critical factor that plays a part in susceptibility to colds is age. A study done by the University of Michigan School of Public Health revealed particulars that seem to hold true for the general population. Infants are the most cold-ridden group, averaging more than six colds in their first year. Boys have more colds than girls up to age three. After the age of three, girls are more susceptible than boy's , and teenege girls average three colds a year to boy’s two.

The general incidence of continues to decline into maturity. Elderly people who are in good health have as few as one or two colds annually. One exception is founds among people in the twentics, especially women, who show a rise in cold infections, because people in this age group are most likely to have young children. Adults who delay having children until thirties forties experience the same sudden increase in cold infections.

The study also found that economics play an important role. As income increases, the frequency at which are reported in the family decreases. Families with the lowest income suffer about a third more colds than families at the lower end. Lower income generally forces people to live in more cramped quarters than those typically occupied by wealthier by wealthier people, and crowding increses the opportunities for the cold virus totravel from person to person. Low income may also adversely influence diet. The degree to which poor nutrition affects susceptibility to colds is not yet clearly established, but an inadequate diet is suspected of lowering resistance generally.

(source: TOEFL reading)

The phrase “in this age group” refers to

A. Infants

B. People in their twenties

C. People in their thirties and forties

D. Elderly people

Điều kiện của x để x+22 chia hết cho 11 là:

A.  x ⋮ 11

B.  x ⋮ 11

C.  x ∈ ∅

D.  x ∈ ℕ

Tính:

Cho hai góc AOx và BOx kề nhau, biết A O x ^ = 36 ° , B O x ^ = 58 ° . Vẽ tia OM là tia phân giác của góc AOx. Tính số đo các góc AOM và MOB.