Which action is an example of the united states using ?

 A. Refusing to trade with a country until it improves its human rights record.

Explanation:  The question asked about using economic influence as a tool of foreign policy.  Trade and commerce are economic activities.  Imposing  trade sanctions against a country is a way of exercising economic influence. In this case, the economic influence is being used to try to achieve a foreign policy goal -- the recognition of universal human rights.

As for the other responses ...

a)scientists

explanation:

the national defense education act had two main goals. the first one was to provide personal that was oriented to defense, including scholars, engineering students and so on. the other goal was to provide financial assistance for the students who would be enrolling at colleges and universities in the 1960s.

answer:

it caused mass african migration, african populations to grow, african empires to topple, and racism against slaves to emerge.

background

early european explorers to the americas likely experienced emotions including awe at the vast "new" environment, amazement at meeting "others," the thrill of the unknown, concern for personal safety, desire for personal reward, and longing for their homeland and those left behind. written and pictorial records attributed to europeans provide the bulk of the records of these early travels. impressions of natives as well as native impressions of europeans are frequently framed in the narratives of the explorers. examination of these records indicates the cautious and curious nature of first encounters.

significance

centuries of ignorance, prejudice, and opinions lacking evidence or scholarly research have tainted traditional views of the earliest meetings between native americans (first nations in canada) and europeans. students may come to recognize how the later period of continued exploration, settlement, and interaction was influenced by these early encounters from the st. lawrence river to georgia.