B is the answer because he is referring to a list of items that he spoke about in his speech. Another key way of identifying this answer is the fact that promise and pledge are synonyms.
The correct answer is A) It acts as a transition to the part of his speech in which he addresses his promises to the country and world.
The purpose of the following short sentence in President Kennedy’s speech is that It acts as a transition to the part of his speech in which he addresses his promises to the country and world.
When President Kennedy says "This much we pledge and more," he has expressed his promises, enumerate some and when heads "and more," he is implying the effort and commitment it is needed to get it done. That there are more things to considerate and with "more" these have to be considered.
