Calfornium-249 Decays to Thallium-205 Through a Series of Nuclear Reactions $\alpha$

Calfornium-249 decays to thallium-205 through a series of nuclear reactions.Only $\alpha$ particles and $\beta$ ^- particles are emitted.How many $\alpha$ particles are emitted?

A) 22
B) 18
C) 15
D) 11
E) 9