Một loài thực vật có bộ nhiễm sắc thể lưỡng bội 2n = 20. Cho hai cây thuộc loài này giao phấn với nhau tạo ra các hợp tử. Giả sử từ một hợp tử trong số đó (hợp tử H) nguyên phân liên tiếp 4 lần, ở kì giữa của lần nguyên phân thứ tư, người ta đếm được trong tất cả các tế bào con có tổng cộng 336 crômatit. Cho biết quá trình nguyên phân không xảy ra đột biến. Hợp tử H có thể được hình thành do sự thụ tinh giữa

A. giao tử (n + 1) với giao tử n.

B. giao tử (n - 1) với giao tử n

C. giao tử n với giao tử n

D. giao tử (n + 1) với giao tử (n + 1).

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

French is the only language other than English spoken on five continents.

A. French and English are the only languages that are spoken on five continents.

B. Unlike French, English is spoken on five continents.

C. French and English are spoken widely in official and commercial circles.

D. Before English, French was the only language spoken on five continents.

Ta có: \(\dfrac{1}{x}\) + \(\dfrac{1}{y}\)=5 \(\Rightarrow\) \(\dfrac{x+y}{xy}\)=5 \(\Rightarrow\) x+y = 5xy (1)

\(\dfrac{1}{x}\) - \(\dfrac{1}{y}\) =1 \(\Rightarrow\) \(\dfrac{y-x}{xy}\)=1 \(\Rightarrow\) y-x= xy (2)

Lấy (1)+(2), ta được: x+y+y-x=5xy+xy

\(\Leftrightarrow\) 2y = 6xy

\(\Leftrightarrow\) 2=6x

\(\Leftrightarrow\) x = \(\dfrac{1}{3}\)(3)

Ta có y-x=xy \(\Leftrightarrow\) y- xy=x \(\Leftrightarrow\) y- \(\dfrac{1}{3}\)y = \(\dfrac{1}{3}\)

\(\Leftrightarrow\) \(\dfrac{2}{3}\)y=\(\dfrac{1}{3}\)

\(\Leftrightarrow\) y = \(\dfrac{1}{2}\) (4)

Từ (3),(4) \(\Rightarrow\) x+y = \(\dfrac{1}{3}\)+ \(\dfrac{1}{2}\)=\(\dfrac{5}{6}\)

Vậy x +y = \(\dfrac{5}{6}\)

Đúng thì tick cho mình 1 cái nha

Đặt phép chia, rồi tính ra. kq= -9

Đúng thì tick cho mình 1 cái nha.

Tui trả lời rầu đó kq là 7,5.Còn nếu tính chi tiết thì ông vào góc học tập của tui mà tìm có trong đó đó.

Đúng thì tick cho tui 1 cái nha.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

As teenagers approach university level, a decision has to be made on what course to pursue. In this world of diversity, (23) ________ such a choice is not easy for both children and parents. In the old days, it was not much a problem to do the task because there were not so many diverse learning areas to choose from. Besides, there were only a few distinctive professional careers like doctor, engineer, accountant, nurse, teacher, etc. to think about. Most higher learning usually led to a financially successful life. (24) ________, the cost of education was not so high.

Today’s world is entirely different from the things (25) ________ have just been described. The job market is constantly changing due to innovative technology and new (26) ________. Meanwhile, most teenagers have difficulty in identifying their own interests. There are a variety of well-organized career talks and student counseling workshops to guide and help teenagers (27) ________ what course to take. Furthermore, psychological tests are also used. Certain instruments such as surveys, interviews and computer software can help to find out preferences, interests, or learning styles of the students.

Điền vào ô trống 24

A. In addition 

B. Otherwise 

C. For example 

D. Therefore