21. Below is a phase diagram for compound X. You wish to purify a sample of X that was collected at P = 1.0 atm and T = 100 by subliming it. In order to sublime the sample, you should (A) increase P to 1.5 atm and then increase T'to 300 K. (B) increase T to 300 K, keeping P = 1.0 atm. (C) lower P to 0.5 atm and then increase T to 200 K. (D) increase T to 300 K and then lower P to 0.5 atm. (E) abandon the attempt to sublime X.