Take a look at the item again:
The potted geranium wilted (A)
from lack of water on Terry's kitchen window
(B) while the faucet dripped
wastefully, (C)
staining the porcelain sink with rust.
You wanted to do this:
The potted geranium wilted from lack of water on Terry's kitchen
window. While the faucet dripped wastefully,
staining the porcelain sink with rust.
The period after window creates a fragment. While the faucet dripped wastefully ... is a subordinate clause, so it cannot stand alone as a complete sentence.
You might want to review the rules.
Go back to the sentence to try again.