Thế mạnh nông nghiệp của vùng trung du và miền núi nước ta là

A. cây lâu năm và chăn nuôi lợn.

B. chăn nuôi gia cầm và cây hàng năm.

C. cây hàng năm và cây lâu năm

D. cây lâu năm và chăn nuôi gia súc lớn

Trường hợp nào sau đây áp suất khí quyển lớn nhất

A. Tại đỉnh núi

B. Tại chân núi

C. Tại đáy hầm mỏ

D. Trên bãi biển

Rút gọn và tính giá trị của biểu thức:  A = 2 x 1 - x 3 + 1 x 2 - x + 1 x 2 + x + 1 khi x = 10

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

        An air pollutant is defined as a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely. Air pollution requires a very flexible definition that permits continuous changes. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled - a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.

        Many of more important air pollutants, such as sulfur oxides, carbon monoxides and nitrogen oxides are found in nature. As the Earth developed, the concentration of these pollutants was altered by various chemical reactions; they became components in biogeochemical cycles. These serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature's output of these compounds dwarfs that resulting from human activities.

        However, human production usually occurs in a localized area, such as a city. In such a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact, the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0. 08 parts per million (ppm), which is about 400 times its natural level. Carbon monoxide, however has a natural level of 0. 1 ppm and is not usually a pollutant until its level reaches about 15 ppm.

According to the passage, human- generated air pollution in localized regions ______.

A. will react harmfully with natural pollutants. 

B. can overwhelm the natural system removing pollutants. 

C. will damage area outside of the localized regions. 

D. can be dwarfed by nature's output of pollutants.

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

        Although speech is the most advanced form of communication, there are many ways of communicating without using speech. Signals, signs, symbols and gestures may be found in every known culture. The basic function of a signal is to impinge upon the environment in such a way that it attracts attention, as, for example, the dots and dashes of telegraph circuit. Coded to refer to speech, the potential for communication is very great. Less adaptable to the codification of words, signs also contain meaning in and of themselves. A stop sign or a barber pole conveys meaning quickly and conveniently.

        Symbols are more difficult to describe than either signals or signs because of their intricate relationship with the receiver's cultural perceptions. In some cultures, applauding in a theater provides performers with an auditory symbol of approval. Gestures such as waving and handshaking also communicate certain cultural messages.

        Although signals, signs, symbols and gestures are very useful, they do have a major disadvantage. They usually do not allow ideas to be shared without the sender being directly adjacent to the receiver. Without an exchange of ideas, interaction come to a halt. As a result, means of communication intended to be used for long distances and extended periods must be based upon speech. To radio, television and the telephone, one must add fax, paging systems, electronic mail, and the Internet, and no doubts but that there are more means of communication on the horizon.

The word “it” in paragraph refers to _______.

A. signal

B. Function

C. way

D. environment

=x(y-3)+2y=11

=x(y-3)+2(y-3)+6=11

=(y-3)(x+2)=11-6

(y-3)(x+2)=5

Vậy (y-3)(x+2) thuộc ước của 5;Ư(5)={-1;1;5;-5}

TH1y-3=1 suy ra y=4 x+2=5 suy ra x=3

TH2y-3=5 suy ra y=8 x+2=1 suy ra x=-1

TH3y-3=-1 suy ra y=2 x+2=-5 suy ra x=-3

TH4y-3=-5 suy ra y=-2 x+2=-1 suy ra x=1

Trong bài thơ" Một khúc ca xuân" nhà thơ Tố Hữu đã viết:

"Đã là con chim, chiếc lá

Thì con chim phải hót, chiếc lá phải xanh

Lẽ nào vay mà không có trả

Sống là cho, đâu chỉ nhận riêng mình".

Cùng quan điểm đó Nguyễn Thành Long đã xây dựng thành công nhân vật anh thanh niên trong truyện ngắn"Lặng lẽ SaPa" từ vẻ đẹp của nhân vật này em có suy nghĩ gì về thanh niên hiện nay.