Is m+z > 0?
1) m - 3z > 0
2) 4z - m > 0
1. It only tells us - m > 3z. But, if both are negative m+3z can be negative. So, not sufficient.
2. Same reason as above. Not sufficient.
1+2. Add both sentences. We get,
z>0. Now, we know z is positive. Using, 1 we can deduct m is positive. Hence, m+z is positive for sure.
Answer = C. Both sentences are necessary.
Am I correct ? What is OA ?
I am ready to fall, but not before I fly.