1) should arrive
2)don’t have to show your
3)shouldn’t worry
4)ought to say goodbye before
5)should not criticise
6)will pay if
7)has a difficulty with making
The answer is D because it states an hypothetical situation, as you explained above.
The subordinate clause is "you must start researching now"
Extraneous means that something is irrelevant or something that has nothing to do with a particular subject. I hope this helps! :)
