Answer:
It is indeed option C for both questions.
Step-by-step explanation:
In the first question, the mistake is letter C for lack of correct punctuation. The structure "like water and air" is an appositive, which means it is added to the sentence to offer more information about a noun - in this case, about "resource". An appositive should be framed by commas, and there is one comma missing. That's where letter C is and, therefore, the reason why it should be checked.
In the second question, the mistake is letter C for improper usage of the conjunction "but". "But" is a coordinating conjunction supposed to introduce an idea that opposes the idea previously presented. In this case, there is no reason to use it because the sentences do not oppose each other, but offer information of the same kind on the same subject instead.