Answer
Please see the work below.
Work Step by Step
We know that
a. If $CF_4$ is in the tank, its not in liquid form as the liquid phase cannot exist above $-46C^{\circ}$.
b. If $C_4H_{10}$ is in the tank, its not in liquid form as $21^C{\circ}$ is above its boiling point $1.0atm$.
