It is found that many insecticides - used to kill insects - lose their effectiveness after some years. What could be the cause of this? A) The insecticides are equally effective - such myths are spread by manufacturers so that they can sell more.

B) The species targeted by the insecticide are destroyed, but new insects which are unaffected, are born.

C) The insects develop resistance to the insecticide, which is passed on to successive generations.

D)The atmosphere contains so much of the insecticide that humans start being poisoned by it.

C) The insects develop resistance to the insecticide, which is passed on to successive generations.

Explanation:

It's called adaptation.

evidence and logical support is essential for a scientist to do in order to maintain credibility. this is because no one can believe without any logic and without any evidence.hence a scientist can maintain credibility by proving himself and by answering logically so experiments prove very beneficial. logical hypothesis give conclusion which is acceptable. therefore, there are two main factors to maintain credibility by a scientist is evidence and logical support.