As you did not state what the question is you just wrote a statement, I am guessing this is a True or False question. If there is more to the question please comment and Id be happy to help you answer more but if this is T/F then Ill answer it here right now.
A main-sequence star maintains a stable size as long as there is enough hydrogen to fuse into helium. True or False?
Answer: True
Hope this Helps, good luck, and comment if you need help on anything else :)