which, witch

Which or which means one of two ( or more )  alternatives--
Which road should we take to the store?
Which of these do you prefer?
Which one?
Which way to the beach?

Which is also used to begin a descriptive phrase--
He had a bad temper, which caused him a lot of trouble.
The house, which she inherited from her mother, was sold yesterday.

Witch or witch ( rhymes with which ) means a person, usually female, who casts magic spells--
She liked to dress up as a witch for Halloween.
He was superstitious, and believed a witch could do magic that would solve his problems.

Now that you know that, you can say--
"Which witch cast the evil spell on us?"

Note--"which" is not used to describe a person --
The man, who stood on the corner, watched them go by.
Her aunt, who was a good cook, taught her to bake.
Note #2--"which" is not a good substitute for "that"--
Bring me the book that is on the table.
He took a night class that included all of the material.
Note # 2--a "witch doctor" is a shaman or a practitioner of traditional or folk medicine--
The old woman had no more confidence in him than in a witch doctor.
Not to be confuse with "which doctor", meaning an inquiry concerning a choice of doctors--
Do you go to that group practice? Which doctor do you see?