After analyzing the conjunctions provided in the answer choices to combine the two ideas, we can form a single sentence as follows:
The astronauts must eat the fresh foods right away because the ISS has no refrigerators.
<h3>What are conjunctions?</h3>
A conjunction is a word used to connect other words, phrases or clauses in a sentence. A subordinating conjunction (as the ones provided) is used, more specifically, to connect two clauses by establishing a relationship of dependency between them.
To combine the two ideas given, the best conjunction seems to be "because". "Because" is used to explain the reason of something. Here, it will be useful to explain why the astronauts have to eat the fresh foods right away.
Learn more about conjunctions:
brainly.com/question/8094735
