What is the difference between digital signature mechanisms and simple encryption?

A.
Digital signatures generally use 128-bit encryption, whereas simple encryption generally uses
56 bits.

B.
Standard encryption mechanisms have no provision for traffic padding to thwart password
sniffers.

C.
Digital signatures carry timestamps, whereas standard encryption does not.

D.
Digital signatures are verified by third parties that vouch for the veracity of the sender and the
contents.