Answer C

Exactly. The issue here is that we are not discussing what occurs when salt is added to a food after it has been microwaved. We are concerned with the effects of salt in food once it has been microwaved. Hope that helps! Please let us know if you have any other questions.

so what is the correct answer here?

I picked answer choice D. The question states that salt reduces the effectiveness of the microwave and killing harmful bacteria... thus if we have food which is prepared with less salt, the microwave will be more effective at killing harmful bacteria which cause food poisoning.

Yes, the correct answer is D and @t3hbar0n is right on point. If salt prevents the microwave from killing bacteria that cause food poisoning, then we can lessen the chance of food poisoning by killing more bacteria by not using so much salt.