3.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、useless
B、endless
C、unless
D、hopeless
While ____ along the shore, I found a lot of sea shells.
A、walk
B、walking
C、to walk
D、walked
It is expected that by 2049 the population of the city ____ two million.