Meaning: To 'discover' means to find out something that was previously unknown.

Wrong options:

• alternative: 'Alternative' is an adjective that describes a different option, which does not fit as a verb in this context.
• different: 'Different' is an adjective that describes dissimilarity, which does not fit as a verb here.
• theorized: 'Theorized' is the past tense of a verb that suggests a hypothesis, which does not match the present tense required in this sentence.
• preferential: 'Preferential' is an adjective that indicates favoring one option over another, which does not fit as a verb.
• acclaimed: 'Acclaimed' is a past participle adjective that means praised, which does not fit the context of an action being taken.

Correct answer: alternative

Explanation: The word 'alternative' serves as a noun in this context, indicating a different method of treatment. It fits grammatically as it aligns with the structure of the sentence, which discusses the use of animals in treatment.

Meaning: An 'alternative' refers to a different option or choice, particularly in the context of treatment methods.

Wrong options:

• discover: 'Discover' is a verb that does not fit as a noun in this context.
• different: 'Different' is an adjective that cannot serve as a noun, making it unsuitable here.
• theorized: 'Theorized' is a verb that does not fit the noun structure required in this sentence.
• preferential: 'Preferential' is an adjective that does not fit as a noun and does not relate to treatment options.
• acclaimed: 'Acclaimed' is a past participle adjective that does not fit the noun form needed in this context.

Correct answer: enhance

Explanation: The verb 'enhance' fits grammatically as it is in the present tense, which is consistent with the ongoing effects of pet ownership. Contextually, it indicates the action of improving the chances of survival after a heart attack.

Meaning: To 'enhance' means to improve or increase the quality or value of something.

Wrong options:

• alternative: 'Alternative' is a noun that does not fit as a verb in this context.
• different: 'Different' is an adjective that cannot serve as a verb, making it unsuitable here.
• theorized: 'Theorized' is a past tense verb that does not match the present tense required in this sentence.
• preferential: 'Preferential' is an adjective that does not fit as a verb and does not relate to improving chances.
• acclaimed: 'Acclaimed' is a past participle adjective that does not fit the action of improving chances.

Correct answer: theorized

Explanation: The word 'theorized' is used as a verb in the past tense, which fits the context of discussing a hypothesis about why pets have positive effects. It aligns grammatically with the structure of the sentence.

Meaning: To 'theorize' means to form a theory or hypothesis about something.

Wrong options:

• discover: 'Discover' is a verb in the present tense, which does not fit the past tense context of this sentence.
• alternative: 'Alternative' is a noun that does not fit as a verb in this context.
• different: 'Different' is an adjective that cannot serve as a verb, making it unsuitable here.
• preferential: 'Preferential' is an adjective that does not fit as a verb and does not relate to forming a hypothesis.
• acclaimed: 'Acclaimed' is a past participle adjective that does not fit the context of hypothesizing.

Correct answer: affection

Explanation: The noun 'affection' fits grammatically as it serves as the object of the sentence, indicating what pets help people to give and receive. It aligns contextually with the emotional connection discussed in the text.

Meaning: 'Affection' refers to a gentle feeling of fondness or liking, particularly in relationships.

Wrong options:

• discover: 'Discover' is a verb that does not fit as a noun in this context.
• alternative: 'Alternative' is a noun that does not fit the context of emotional connection.
• different: 'Different' is an adjective that cannot serve as a noun, making it unsuitable here.
• theorized: 'Theorized' is a verb that does not fit the noun structure required in this sentence.
• preferential: 'Preferential' is an adjective that does not fit as a noun and does not relate to emotional connections.
• acclaimed: 'Acclaimed' is a past participle adjective that does not fit the noun form needed in this context.