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

While my mother _________ a film on TV, my father was cooking dinner. It was March 8^th yesterday.

A. watched

B. was watching

C. had watched

D. watches

Tìm giá trị của a để hai đường thẳng y = (a – 1)x + 2 (a ≠ 1) và y = (3 – a)x + 1 (a ≠ 3) song song với nhau.