Answer:c
Explanation:I just did it on usatestprep
The subordinate clause is : " which had been dumped into the city water system "
Allusion is the type of figurative language used here, I believe.
"All of a sudden..." is a transition that shows suspense. It says something happened, but it didn't happen with any warning and it doesn't tell the reader up front what went on or if it was good or bad.
