Which group of words is a sentence rather than a fragment?

A.
Cicadas live only one month.

B.
By fastening themselves securely to tree trunks to molt their outer cases.

C.
Trying to stay out of sight, move around a branch, hiding from view.

D.
Work their way a few centimeters into the soil and feed on the sap of tree roots

A. Cicadas live only one month.