A, B, C là 3 điểm thẳng hàng. Đặt vật ở A, một thấu kính ở B thì ảnh thật hiện ở C với số phóng đại k 1 = 3 . Dịch thấu kính ra xa vật đoạn l = 64 cm thì ảnh của vật vẫn hiện ở C với số phóng đại k 2 = 1 3 . Tính f và đoạn AC.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Leave it in the oven until it __________ brown

A. turns

B. colours

C. changes 

D. cooks

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 from 23 to 27.

        No one can know when sports began. Since it is impossible to imagine a time when children did not spontaneously run races or wrestle, it is clear that children have always included sports in their play, but one can only speculate about the (23) _________of sports as autotelic physical contests for adults. Hunters are depicted in prehistoric art, but it cannot be known (24) _____ the hunters pursued their prey in a mood of grim necessity or with the joyful abandon of sportsmen. It is certain, (25) _________, from the rich literary and iconographic evidence of all ancient civilizations that hunting soon became an end in itself at least for royalty and nobility. Archaeological evidence also indicates that ball games were common among ancient peoples as different as the Chinese and the like those recommended for health by the Greek physician Galen in the 2^nd century AD.

Điền vào số (24)

A. when     

B. whether  

C. how       

D. why