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 $\beta$ ^- particles are emitted?

A) 11
B) 9
C) 7
D) 3
E) 5