Identify the function of the suffix or word in each sentence.

The suffix "-ly" is typically added to adjectives to form adverbs, which describe how an action is performed.
The correct option is C.

$$\boxed{\text{C. makes an adverb}}$$

The suffix "-er" is used to form the comparative degree of adjectives, comparing two things.
The correct option is D.

$$\boxed{\text{D. -er}}$$

The suffixes "-ness," "-ion," and "-tion/-sion" are all used to form nouns. The suffix "-es" is primarily used to form plural nouns or as a third-person singular verb ending, not to derive a noun from another word class.
The correct option is C.

$$\boxed{\text{C. -es}}$$

"Should" is used to give advice or make a recommendation.
The correct option is D.

$$\boxed{\text{D. should}}$$

"Mustn't" expresses a strong prohibition or a rule that something is not allowed.
The correct option is B.

$$\boxed{\text{B. mustn't}}$$

"Don't have to" indicates that something is not necessary. Since the deadline is extended, rushing is not required.
The correct option is B.

$$\boxed{\text{B. don't have to}}$$

"Must" expresses a strong obligation or necessity.
The correct option is A.

$$\boxed{\text{A. must}}$$

"Will" is used to express a future intention or a necessary action to achieve a goal.
The correct option is D.

$$\boxed{\text{D. will}}$$

"Ought to" expresses a moral obligation or strong recommendation, similar to "should."
The correct option is B.

$$\boxed{\text{B. ought to}}$$

"Which" is the correct relative pronoun to refer to a thing (the book).
The correct option is B.

$$\boxed{\text{B. The book which I borrowed from the library is very interesting.}}$$

"Whose" is a possessive relative pronoun, indicating that the students belong to the teacher.
The correct option is C.

$$\boxed{\text{C. whose}}$$

"Where" is the correct relative adverb to refer to a place (the village).
The correct option is C.

$$\boxed{\text{C. where}}$$

"Whom" is the object form of "who" and is used when the pronoun is the object of a verb or preposition (I consulted whom).
The correct option is D.

$$\boxed{\text{D. whom}}$$

"Who" is the subject form of the relative pronoun, referring to the teacher who performs the action of teaching.
The correct option is A.

$$\boxed{\text{A. who}}$$

"Where" is the correct relative adverb to refer to a place (the vehicle) where an action occurred.
The correct option is B.

$$\boxed{\text{B. where the gun was found}}$$

"Whom" is the object of the preposition "to."
The correct option is B.

$$\boxed{\text{B. to whom}}$$

The present perfect tense ("has lost") is used to describe an action that happened in the past but has a present result (she can't find them now).
The correct option is B.

$$\boxed{\text{B. has lost}}$$

"Yet" is commonly used with the present perfect tense to indicate that something has not happened up to the present moment. "We" takes "have."
The correct option is A.

$$\boxed{\text{A. haven't eaten}}$$

"For" is used to specify a duration of time.
The correct option is C.

$$\boxed{\text{C. for}}$$