is this a fragment; The panther lay motionless behind the rock. Waiting silently for its prey

One is a fragment. One is a sentence. Do you see which is which?

Yes, it is a fragment.

No, the given sentence is not a fragment. It is a complete sentence as it contains a subject ("The panther") and a predicate ("lay motionless behind the rock, waiting silently for its prey").

Yes, the given sentence "The panther lay motionless behind the rock. Waiting silently for its prey" is a fragment. It consists of two separate clauses that are not properly connected. The first clause "The panther lay motionless behind the rock" can stand alone as a complete sentence, but the second clause "Waiting silently for its prey" cannot stand alone and does not have a subject.

To fix this fragment, you can combine the two clauses with appropriate punctuation or a coordinating conjunction.

For example:
"The panther lay motionless behind the rock, waiting silently for its prey."
or
"The panther lay motionless behind the rock and waited silently for its prey."