The people believed there was a (n) _____ level of pollution in the water until the mayor ______ it
[A].
innocuous - challenged
[B].
unhealthy - confirmed
[C].
harmless - encouraged
[D].
contagious - overruled
[E].
dangerous - surcharged
Answer: Option A
Explanation:
Until this sentence implies a shift in that belief that there was an innocuous (harmless) level of pollution at the point that it was challenged by authority.