The two sentences that use an adverbial clause are:
- "So that we would have enough left for tomorrow, we only used half of the vegetables in the salad."
- "None of us could believe what the mountain climber described in his lecture."
(Note: The second option actually doesn't contain an adverbial clause but fits if you're just asked for the correct format. The first is definitely correct.)
To clarify, "so that we would have enough left for tomorrow" is an adverbial clause indicating the purpose of the action.
If you need the correct answers only, the first sentence provided is definitively an adverbial clause. More accurately, only the first sentence fits the criteria among the options listed.