DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Instead, DDT is largely useless against many insects because they are resistant. Propose a hypothesis as to why these organisms have become resistant to the chemical.

None of the individual insects should have possessed genomes that made them resistant to DDT.

Explanation:

Pesticides such as DDT have been considered one of the best way to kill insects in the past. But with time, farmers have observed that this is not an authentic method. This is because the insects can gain resistance to the pests if they are exposed to the pesticide again and again. Even they could transmit these resistant genes in their offsprings. Hence, DDT will become useless against insects over time.  

the tricuspid valve is present between right atrium and right ventricle

the answer is c. it will give up it's valence electron to the other atom.