Answer 1) Option B) Shift to the right.
Explanation : If the amount of land available to the company increases, the PPC will shift to the right. As the graph indicates, the PPC will grow by shifting on right side as the company is acquiring more land for building purpose.
Answer 2) Option C) Remain Unchanged.
Explanation : The company realizes it cannot construct any buildings on a portion of the land because it is at risk of a cave-in.
In this case, the PPC will remain unchanged. When the company realizes that no construction can be done on the portion of land because of its hollowness the PPC will remain to be undisturbed.