hey,
the above is true, of course, but this is one of those situations where examples are necessary.

i presume you're talking about stuff like this:

xxxxxxxxxxxxxxxx?

(1) |x| = x
(2) x is positive

in this case, statement 1 means "x is either positive or 0" (make sure you understand why). so, statement 2 is just a sub-case of statement 1. in this case, you can eliminate C (since putting these statements together is the same as just saying #2) and A (since if #1 is sufficient, then #2 is automatically sufficient as well).

--

by the way --
if you once had a habit of picking (c) on these kinds of problems, then the problem almost certainly has nothing to do with "tricks". instead, in that case, the problem is most likely that you just haven't internalized the DS process well enough.

i.e., if one or the other of the individual statements is already sufficient to solve the problem, then you don't ever get to the stage where (c) is even an option.
the only time (c) and (e) are even on the table is when you've already determined that neither of the individual statements will solve the problem alone.