As far as scientists can tell, *there is no connection between these two events* A) Main clause
B) Subordinate clause

lets none because you provide no details.

the correct answer is d.   to change the pace

explanation:

hello!

unfortunately i cannot answer your question because there is no question.

to get a fast reply and accurate results, re-post (or edit) the question to add a question.

sorry!

i think the first one, it makes the most sense.