Not Just a Croak (1) Scientists know that male bullfrogs talk to other bullfrogs by croaking. (2) Recent studies, however, show that the croak is more complicated than it sounds. (3) Researchers at Brown University say the bullfrog's croak can include a series of stutters. (4) Researchers believe the pattern of the stuttering determines what the frog is saying. (5) All of the croaks that were studied began with no stutter at all. (6) Then, as the croaking continued, various sorts of stuttering occurred. (7) The researchers say the stuttering pattern can be quite complex, suggesting that frogs have an impressive vocabulary!

Choose the best place to add the following sentence.

Among other things, they croak to stake out their territory.
A.
before sentence 4
B.
after sentence 1
C.
before sentence 7
D.
after sentence 5