And his answer trickled through my head like water through a sieve meaning 1. the speaker's head was empty
2. the man's ideas flowed rapidly
3. the answer amused the speaker
4. the answer was quickly forgotten ​

The awsner should be : b

The poem is an unconventional sonnet; it develops a main idea in the first twelve lines, and is capped by a big thought in the final couplet. the poem follows a narrator describing the industriousness of nature’s creatures, preparing for the coming spring. all of creation is at work, but the speaker is sullen as the only creature he can see who finds himself without an occupation.