Which is the best use of punctuation? a. many people are squeamish around, insects, and rodents. b. our instructor taught us techniques (to us) master welding. c. upon hearing her diagnosis, she was filled with one emotion: relief. d. the children in her afterschool class tend to be immature (and silly).

The best use of punctuation is C, "upon hearing her diagnosis, she was filled with one emotion: relief". "Upon hearing her diagnosis" could be understood as the cause of her relief or as modifier of time of the whole sentence ("she was filled with one emotion: relief"), that is why that PP is separated from the rest of the sentence. Then, emotion and relief are a clear example of a term-specification clause. The term would be "emotion" and the specification of it would be "relief", relief is the emotion felt by her.  

A is punctuated as if it was a list but the coordinated elements do not belong to the same word category. It would be correct if it read "many people, insects and rodents are squeamish around".  In B and D, the parenthesis is not necessary. The information contained by them is not extra information but required information to understand the meaning of the sentence.

the answer is a 100% b) communism

hope dis ya ; )