Answer:
I would have to say <em>e</em><em>fforts</em><em> </em>is the modifier in this sentence since the word isn't being used in correct context.
Revision: Distressed at the possibility of others hearing them, <em>changes</em> were made to be very quiet in the annex.
A. analytical
definition of analytical: Relating to or using analysis or logical reasoning
I think a. use of verb tenses
"think"