C、They don't experience separation anxiety as dogs do.
D、They respond to their owners’ voices less than dogs do.
While ____ along the shore, I found a lot of sea shells.
A、walk
B、walking
C、to walk
D、walked
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.