Extremely High Temperatures Were Required to Initiate Nuclear Fusion,but,once Started,large

Extremely high temperatures were required to initiate nuclear fusion,but,once started,large amounts of energy were released while fusion reactions of lighter nuclei formed isotopes up to ⁵⁶Fe.This is analogous to __________

A) boiling a liquid by heating it.
B) melting a solid by heating it.
C) lighting a match to start a fire.
D) two magnets attracting each other.
E) lifting a mass against gravity.