Hi,
In this question, we are asked to fill in the additional advantage of the Hydraulic tools, which must be different from the first one, over the old tools. Be minded that we need to find an
additional reason to choose Hydraulic tools because of the conjunction couples: not only ... but also.
So let's evaluate each choice.
A - One hydraulic rescue tool can perform the functions of both a crowbar and a circular saw. => already mentioned as a premise in the argument -> eliminate A
B - Hydraulic tools are quieter and do not cause crash victims to panic. => already mentioned as the first reason for choosing the Jaws over the others. -> eliminate B
C - Hydraulic tools are unlikely to complicate an already dangerous situation in the way that more traditional tools often did. => matched what we are looking for -> keep this choice
D - Hydraulic tools are able to quickly and efficiently repair structural damage to vehicles involved in collisions. => the argument is about tools to remove victims from crashed vehicles so this choice is out of scope -> eliminate D
E - Emergency response workers have greater leverage when using hydraulic tools than when using traditional tools, such as crowbars and circular saws. => more leverage then what? this choice does not provide a clear edge of using Hydraulic tools > eliminate D
Only C is left.
Hope this helps.