Meaning: 'Conducting' means to carry out or manage an activity or process.

Wrong options:

• remained: The word 'remained' is a past tense verb that implies a state of being unchanged, which does not fit the context of actively managing a social experiment.
• reciprocating: 'Reciprocating' is a verb that means to respond to an action with a corresponding one, which does not apply to the context of conducting an experiment.
• analyze: 'Analyze' is a verb that means to examine in detail, which does not fit as it does not convey the action of carrying out an experiment.
• declined: 'Declined' is a past tense verb indicating a decrease, which does not fit the context of conducting an ongoing experiment.
• meanwhile: 'Meanwhile' is an adverb used to indicate something happening at the same time, which does not fit as it does not describe an action related to the experiment.

Correct answer: declined

Explanation: The word 'declined' is the past tense of 'decline,' which fits grammatically as it describes a decrease in the share of national income over a specified period. It is contextually appropriate as it refers to the change in income distribution.

Meaning: 'Declined' means to have decreased or diminished in quantity or quality.

Wrong options:

• conducting: 'Conducting' is a present participle that does not fit here as it describes an action rather than a change in income.
• remained: 'Remained' suggests no change, which contradicts the context of a decrease in income share.
• reciprocating: 'Reciprocating' does not relate to income changes and is irrelevant in this context.
• meanwhile: 'Meanwhile' is an adverb indicating simultaneous events, which does not fit as it does not describe a change in income.
• analyze: 'Analyze' is a verb that does not fit the context of describing a decrease in income.

Correct answer: meanwhile

Explanation: The word 'meanwhile' serves as a transitional adverb that indicates a simultaneous occurrence with the previous statements about income distribution. It fits grammatically and contextually, linking the ongoing changes in income shares.

Meaning: 'Meanwhile' means at the same time or during the same period.

Wrong options:

• conducting: 'Conducting' is a verb that does not fit as it describes an action rather than a transitional relationship between events.
• declined: 'Declined' is a past tense verb that does not serve as a transitional phrase and does not fit the context of timing.
• reciprocating: 'Reciprocating' does not relate to the context of timing and is irrelevant here.
• analyze: 'Analyze' is a verb that does not fit as it does not indicate a simultaneous occurrence.
• limit: 'Limit' is a verb that does not serve as a transitional adverb and does not fit the context.

Correct answer: limit

Explanation: The word 'limit' is a verb that fits grammatically as it indicates an action that the United States has not taken sufficiently. It is contextually appropriate as it refers to the action of reducing economic inequality.

Meaning: 'Limit' means to restrict or reduce something.

Wrong options:

• conducting: 'Conducting' is a present participle that does not fit as it describes an action unrelated to reducing inequality.
• declined: 'Declined' is a past tense verb that does not fit as it does not indicate an action to reduce inequality.
• reciprocating: 'Reciprocating' does not relate to the context of limiting inequality and is irrelevant here.
• meanwhile: 'Meanwhile' is an adverb that does not fit as it does not describe an action related to economic policies.
• analyze: 'Analyze' is a verb that does not fit the context of taking action to limit inequality.