Answer i will give the brainliest for the correct one hurry

in which of the following sentences is the phrase underlined?

i my younger brother build a sand castle at the beach.

my brother dug a giant hole using only a small pail and shovel.

after we built a sand castle, we jumped into the ocean for a swim.

at high tide, our sand castle was washed away by the waves

a
b
c
d