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

I _____ at the exam paper lying on Mr. Gregson’s desk, but I didn’t want to risk it.

A. could look

B. can have looked 

C. can look

D. could have looked

1. Cau tao ngoai:

-than hinh thoi: lam giam suc can khong khi' khi bay

-chi truoc bien doi thanh canh:co tac dung nhu quat gio va can khong khi' khi ha canh.

-chi sau co 3 ngon truoc, 1 ngon sau, co vuot: giup chim bam chat vao canh cay khi chim dau va khi ha canh .

-long onng co cac soi long tao thanh phien mong:lam cho canh chim khi dang rong ra tao nen 1 dien tich rong.

-long to co cac soi long manh: giu nhiet va lam than chim nhe.

-mo sung bao lay ham khong co rang: lam dau chim nhe

-co dai khop voi than: phap huy tac dung cua giac quan, thuan loi khi bat moi, ria long.