Which of the following is a good example of heterothallism?

Q. Which of the following is a good example of heterothallism?
A. Spirogyra
B. Rhizopus
C. Pinus
D. Castor bean
Answer: Rhizopus

A. Spirogyra
B. Rhizopus
C. Pinus
D. Castor bean
Answer: Rhizopus