Because they don't try hard enough.
No, you probably won't fail computer science. Probably. Mathematics involves logic and problem solving - which is a major part of computer science. Although programming is also a big part of computer science, there are quite a lot of branches to do with computers, and you don't necessarily have to work with programming. I'm good at maths and not so good at programming but I still did pretty well (better than all the hard-core programmers) in the computer science / programming class. If that's any consolation.
A student may fail mathematics because he/she did not study, did not attend class, or did not understand the lesson material.
No, there is no reason why you should fail in this case.
No you will not fail.
Not true. Chemistry is easier than Mathematics.
Not you will but you can.
No.
A student may fail mathematics because he/she did not study, did not attend class, or did not understand the lesson material.
It depends on what you mean. If you mean "more likely to fail chemistry and physics than to fail mathematics", then the answer is presumably yes. If you mean "more likely to fail chemistry and physics than some bozo who can't figure out how this 'multiplication' thing works", then no. In physics and (most kinds of) chemistry, a solid understanding of mathematics can only be helpful.
no
You'll certainly not fail physics BECAUSE you are good at math - you NEED math for physics and engineering.
yes of course