The question says which option is strongest objection to the argument above
that means we need to choose the Most opposite choice against the meaning of given argument ..
here among these choices , choice D
- The time since the beginning of the use of the pesticide has been too short to allow some of the predicted effects to occur.
satisfy our goal . In the question there is a large time limit 1991 to 1996 but our choice D says the time when use of pesticide begin till now is too short time to see how those pesticides behaves , which is false and also better way oppose the argument than other three options .
Hence the correct answer is D .