The conclusion is that this investment has been bad.
We need to weaken,
therefore,
we need to say that this investment has been worthwhile.
This talks something good about the currently used pesticides.
So, this cannot  weaken, this will only strengthen the argument
that the investment was not worthwhile. We need an answer
choice that tells something good about the new
pesticide. This further criticizes the new pesticide, so, this
cannot weaken the conclusion. This is a fact that a certain
part of the taxpayers' money be dedicated but it should be used
for useful activities.
This cannot be the right choice.
This doesn't weaken.
This is a very abstract choice; fine, later on,
it happens that skepticism is later met by acceptance, but
there has to be some merit, there is no merit shown in the
argument so far, this cannot be a fine weakening statement.
This talks about some positive that the effect lasts
considerably longer.
Suddenly,
we have something positive to convey and, therefore, the conclusion
is weakened.
E is the best choice.
