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
The writer's first book is____ popular than his second one.
A、so
B、less
C、such
D、much
Pets____constant care are not suitable for people with little spare time.