What is the speaker describing in these lines from “the nymph's reply to the shepherd”? time drives the flocks from field to fold, / when rivers rage and rocks grow cold, / and philomel becometh dumb….
a. the coming of winter
b. the end of love
c. a new pleasure to experience
d. marriage

a. the coming of winter.

In these lines, the speaker describes the coming of winter. He states how, as the winter comes, the flocks of sheep go from the fields to the stables, to protect themselves from the weather. The rivers get more violent and the rocks colder. "Philomel" refers to the nightingale, so the line "and philomel becometh dumb" means that the birds have stopped singing. All of these describe how nature changes in winter.

a) walter looks unhealthy