She wondered if the water was not … hot for drinking.

Analyze the question: The sentence is "She wondered if the water was not __ hot for drinking." We need a word that fits with "hot for drinking," showing a degree that makes the water unsuitable.

Concept: The structure too + adjective + for + noun/gerund expresses an excess: more than is needed or acceptable. For example, "The tea is too hot for drinking" means it is so hot that it cannot be drunk.

Testing each option:

• A. very: "not very hot for drinking" is awkward. "Very" does not link naturally with "for drinking" to show a result or limit.
• B. so: "so hot for drinking" is incomplete. "So" needs a result clause such as "so hot that...".
• C. much: "not much hot" is ungrammatical. "Much" cannot directly modify an adjective like this.
• D. too: "not too hot for drinking" is correct. It means she wondered whether the water was excessively hot and therefore unsafe to drink.

Correct sentence: She wondered if the water was not too hot for drinking.

Tip: Whenever you see an adjective followed by "for + something/doing something", think of "too." Remember: too + adjective + for/to = more than enough, so a problem arises. Examples: "too tired for work," "too heavy to lift."