What is the only way that a white dwarf can suddenly explode as a supernova?

What is the only way that a white dwarf can suddenly explode as a supernova?

A. if another star collides with it

B. if it passes through a large dust cloud

C. if it has a companion star that transfers mass to it causing it to have more mass than 1.4 Msun

D. if it collapses as a black dwarf