How should the original use case be linked to the new use case?

A business analyst has identified that one of the use cases on a use case diagram contains a large amount of optional processing. This optional processing is so large that he has decided to remove it to a separate use case which can be called by the original use case if required.

How should the original use case be linked to the new use case?
A . By a broken, arrowed line stereotyped with the word «include».
B . By a broken, arrowed line stereotyped with the word «uses».
C . By a solid line with no arrowhead or stereotype.
D . By a broken, arrowed line stereotyped with the word «extend».

Answer: D