2 goes with the second one (control rods).
3 goes with forth one (mass of unstable fuel)
4 goes with one (shield)
1 goes with third one (moderator)
5 goes with coolant
My best bet would to go with 'were' because they sound similar and it just seems more professional.
A. Never use words like I, I’ll, we or you in an essay unless you are asked to write in the first person.
The importance would be all the time and effort he put into it but know that he is dead he would have someone to take over
