Meaning: 'Splurged' means to spend money freely or extravagantly, especially on something enjoyable or luxurious, like a live lobster for dinner.

Wrong options:

• massaged: 'Massaged' refers to the act of manipulating the body, which does not fit the context of spending money on food.
• clapped: 'Clapped' means to strike the hands together, typically in applause, which is unrelated to the context of dining or spending.
• disinterred: 'Disinterred' means to dig up something that was buried, which is not relevant to the act of spending money on a meal.

Correct answer: believed

Explanation: The word 'believed' is the past tense of 'believe,' which fits grammatically and contextually as it indicates what researchers thought in the past about crustaceans' ability to feel pain. It aligns with the sentence structure and the overall narrative about changing perceptions in research.

Meaning: 'Believed' means to accept something as true or real, in this case, the researchers' previous understanding of crustaceans' nervous systems.

Wrong options:

• breech: 'Breech' is a term that refers to the back part of something, often used in a different context, and does not fit grammatically or contextually here.
• beast: 'Beast' refers to an animal, typically a large or dangerous one, which does not make sense in the context of researchers' thoughts.
• fricasseed: 'Fricasseed' is a cooking term that means to cook meat in a sauce, which is irrelevant to the context of researchers' beliefs.

Correct answer: previously

Explanation: The word 'previously' is an adverb that indicates something that happened before a certain point in time. It fits grammatically and contextually as it modifies the verb 'thought,' indicating the prior belief about crustaceans' sensitivity to pain.

Meaning: 'Previously' means at an earlier time or before now, referring to the earlier beliefs held by scientists about crustaceans.

Wrong options:

• tediously: 'Tediously' means in a manner that is boring or tiresome, which does not fit the context of discussing past beliefs.
• irremediably: 'Irremediably' means in a way that cannot be corrected or remedied, which does not logically connect to the context of changing beliefs.
• immediately: 'Immediately' means at once or without delay, which does not relate to the concept of past beliefs.

Correct answer: experienced

Explanation: The word 'experienced' is the past participle of 'experience,' which fits grammatically as it describes the crabs undergoing a specific event (the electric shock). It aligns with the context of the sentence, indicating what the crabs went through during the study.

Meaning: 'Experienced' means having gone through or encountered something, in this case, the crabs encountering an electric shock.

Wrong options:

• threatened: 'Threatened' means to be in danger or to warn of harm, which does not fit the context of the crabs undergoing a shock.
• renounced: 'Renounced' means to formally give up or reject something, which is not applicable to the context of the crabs' reactions.
• persuaded: 'Persuaded' means to convince someone to do something, which does not relate to the crabs' experience of shock.

Correct answer: eventually

Explanation: The word 'eventually' is an adverb that indicates something happening at a later time. It fits grammatically and contextually as it describes the outcome of the crabs learning to avoid the hiding place after experiencing the shock.

Meaning: 'Eventually' means at a later time or after a period of time, indicating that the crabs learned to avoid the hiding place over time.

Wrong options:

• carnivorously: 'Carnivorously' means in a manner related to eating meat, which does not fit the context of learning behavior.
• treacherously: 'Treacherously' means in a way that is dangerous or deceptive, which does not apply to the learning process described.
• cryptography: 'Cryptography' refers to the practice of secure communication, which is unrelated to the context of animal behavior.