Answer:
I believe its D.
Explanation: I hope its correct.
"The space shuttles is the subject."
Simple formula: find the verb of the sentence then ask the question "who or what performs the verb" and the answer to that question is the SUBJECT of that sentence!
In your sentence; ask the question;
"Who or what have made travel to the International space station convenient and possible?
Answer: The space shuttles (that's your subject)
Answer:
D. Or C.
Explanation:
Make sure that the reader would understand the letter and make sure to illustrate your topic
