2. In each of the following groups of words, there are four underlined letters or letter combinations marked A, B, C and D. Compare the underlined parts and identify the one that is different from the others in pronunciation.
A、there
B、thick
C、thank
D、thirty
If John had entered the office ten minutes ago, he____ what we were talking about just now.
A、should know
B、had known
C、would know
D、would have known
Tom is a careless person. He forgot ____ the door again when he went out yesterday.