When does contributory liability exist in patent law?

Select one:

a. Contributory infringement exists whenever someone sells a component of a patented invention that has only one substantial noninfringing use.

b. Contributory infringement exists when someone knowingly sells a component of a patented invention that has no substantial noninfringing uses.

c. Contributory infringement exists whenever someone knowingly induces someone else to engage in indirect infringement.

d. Contributory infringement exists whenever someone unknowingly induces someone else to engage in indirect infringement.