Major Technical Obstacle(s) to the Achievement of a Controlled Fusion

Multiple Choice

Major technical obstacle(s) to the achievement of a controlled fusion reaction is (are)
I. attaining a temperature of at least 1.0 ´ 108 K
II. containment of the plasma long enough to generate a net output of energy
III. recovering the energy in some useable form

A) I only
B) II only
C) III only
D) I, II, and III
E) I and II only