Which sentence uses the superlative form of an adverb?

AOf all the boats on the lake, the swan boat moved most slowly.

BLittle crabs scurried quickly over the sand.
CMy cousin's boat sailed closer to the sandbar than my boat.
DI always like to visit my grandmother.

Verified Answer :

a. Of all the boats on the lake, the swan boat moved most slowly.
the 
superlative form of an adverb is most word-ly 
in this case it's most slowly

A. Of all the boats on the lake, the swan boat moved most slowly.

the superlative form of an adverb is most word-ly

in this case it's most slowly.