Which of the following diagrams (figure) depicts ideal gas behaviour?

      

1. (a), (c)
2. (a), (d)
3. (c), (d)
4. (a), (b)

(1) Hint: Use the ideal gas equation.
We know that the ideal gas equation is PV =nRT
Step 1: Find the correct condition in each option.
(a) When P=constant, volume V  Temperature T
(b) When T = constant, pV = constant
So, the graph is a rectangular hyperbola.
(c) When V = constant, p  T
So, the graph is a straight line passes through the origin.
(d) pVT
 pVT = constant
So, the graph, hence, passes through the origin.
So, (d) is not correct.