Problem One
It sure isn't D. That would be a positive reason for texting. This is an essay against texting. It may be true, but you want to hide it from prying eyes who might use it as an argument against your thesis.
I don't know how you could prove the second part of B. In any event the detail you need has to support the idea that you are endangering others. Your problem with germs doesn't affect me, especially through cyber space.
You could pick A, but the problem is the second part of the choice. You'd really have to work to show how that could happen although I suppose it is possible. If it can cause misunderstandings, then that would happen whether you were texting or having a friendly game of Badminton.
I think C is the better answer, but I'm not fully convinced it isn't A. That's the problem with multiple guess. Eventually it does break down to a guess sometimes.
Problem Two
You can get rid of A for certain. It may be true, but it has nothing to do with stiff necks and calloused thumbs.
Same comment applies to B.
I don't think you are really talking about limiting texting. You are talking about not changing your current habits. So C is marginally incorrect.
Pick D
Their
I think that's what you're asking for?
In the book <em>To Kill a Mockingbird,</em> we meet Aunt Alexandra, Scout's aunt. Scout often clashes with her aunt because of the different ideas that each one of them have about what it means to be a girl.
Aunt Alexandra is very traditional, and she believes that a girl should behave in a lady-like way. This includes wearing dresses, caring about reputation, not playing rough, not climbing trees and playing with dolls. Scout, however, dislikes all of these things and it causes her great frustration to have to deal with the ideas of her aunt.
I am not sure about the complete question what you mean but i think it is 1) can not be used to correct most run-on sentences.