4.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、cool
B、flood
C、food
D、moon
It is expected that by 2049 the population of the city ____ two million.
A、would reach
B、will have reached
C、will be reaching
D、would have been reached
How does exercise sharpen the mind according to Para.2?