These are logical arguments for which you are being asked to test the validity. Each line prior to the conclusion represents a separate premise and the premises are conjoined . An easy way (not involving full truth tables) is sometimes called "the method of backward fell swoop" (ref Quine) in which you take the truth value of the conclusion to be false and show how this would make the premises false. You must
however learn the four basic truth tables ( for conjunction, disjunction, negation and implication) in order to do this exercise.
For example in no.4, assume C =0 (false), this would make E=0 in the second line, which would make B=0 in the first line. Then the fourth line which implies B=1 would be a contradiction. So validity has been proved since C=1 is the only way to avoid a contradiction.