Answer
Please see the work below.
Work Step by Step
We know that
a. We know that when the gas is compressed at $20^{\circ}C$, it will condense into a liquid as $20^{\circ}C$ is above the triple point but below the critical point.
b. When the gas is compressed at $-70C^{\circ}$, it will condense directly to the solid phase as the temperature of $-70C^{\circ}$ is below the triple temperature.
c. When the gas is compressed at $40^{
circ}$, it will not condense as $40^{\circ}C$ is above the critical point.
