Q: Think of a five-letter word starting with T. The word is plural. Add an S at the end, and you'll get a six-letter word that is also plural. What words are these?Indeed, what are these words? I can only think of one at the moment... I'll give you the second word after the session expires.
Edit: If you read the question carefully, I found it already contained a clue to the first word ("What words are these?") and then there were some hints in my comments. In case you missed them, read the following: "I'll give you the second word after the session expires." Did you catch those hints?
A: THESE (plural of "this")
THESES (plural of "thesis")