Disclaimer: I just answered this, here is the answer again!
*Used copy paste from my own answer as it is a repeated question, no copied work*
3. A
The relation between V and I at constant R is;V=IR, so it is a direct linear relation.
4. A
This is another direct linear relation as P=IV.
5. D
The relation between P, R, and V is P=, so P is inversely proportional to R.
6.B
The relation between P,I, and R is , so P is directly proportional to the square of I.
Please note that y:x relations are always straight lines while relations are parabolic lines.
Hope this helps!