Which of the following choices creates the most logical transition within sentence 2 (reproduced below)? It may be too soon to start planning your Martian vacation, however there are good reasons to doubt that humans will be able to undertake long-distance space flights in the foreseeable future.

It's A. (as it is now)

Explanation:

Just did the test

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.

go i think this should he the answer i'm not sure