sorry about that.I don't know the rules here.These are the subjects of TOFEL but not homework.
The following is what I thought about the answer.
1.The word "superseded" means "be better than ,which doesn't make sense in the context of Sentence 1. The rest is fine (assuming insistent wasn't mis-spelled)..
2.There is NOTHING wrong with Sentence 2. ("26 years of age" is
Welcome to the forums. I would change the first sentence to:
The irritable sergeant was insistent that nothing supersede the drilling of the forty new men. In this case supersede doesn't mean "to be better than," but rather "to replace."