plz post your reasoning can we use decimal numbers to

mandy,
If it does not say numbers must be integers, then yes, you can try using decimals or fractions.

Anyway,

I am getting (C)

ST1. A-C-B is even, or A-C-B=2k

If we choose A,B,C all integers and even, then A+B+C is even
However, if we use fractions, it does A+B+C does not have to be even

Let's see: A=2.2, B=0.1, C=0.1 and A-B-C=2 even. But A+B+C is not

ST2. (A-C)*B is odd

It follows that either
(1) A-C is even and B is odd
or (2) A-C is odd and B is even
or (3) A-C is a fraction and B is integer such that (A-C)*B=odd
or (4) A-C is integer and B is a fraction such that (A-C)*B=odd

Not sufficient.

Now, combine ST1 and ST2.

Neither A-C nor B can be fractions, otherwise ST1 is not valid.

So, all numbers -- A, B, and C -- must be integers.

Moreover, either 1 or all 3 must be odd (otherwise ST2 is violated.)

Therefore, A+B+C is even

(C) is sufficient