When I was down beside the sea

A wooden spade they gave to me

To dig the sandy shore.

My holes were empty like a cup.

In every hole the sea came up

Till it could come no more.

—“At the Sea-Side,”
Robert Louis Stevenson

What is the central idea of the poem? Choose the best answer.

A. The beach is a dangerous place.
B. Our work will all be washed away, but it is not a sad thing.
C. The ocean is a mean and uncaring part of nature.
D. It is sad to think that every person’s work will eventually be washed away.