Cho tam giác cân ABC (AB = AC), vẽ các đường cao BH, CK (h.66).

a) Chứng minh BK = CH.

b) Chứng minh KH // BC.

c) Cho biết BC = a, AB = AC = b. Tính độ dài đoạn thẳng HK.

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions.

There are many TV commercials which distracting viewers from watching their favorite films.

A. economics       

B. businesses        

C. contests  

D. advertisements