Assume That a Planet Just Like Earth Orbits the Bright $\odot$

Multiple Choice

Assume that a planet just like Earth orbits the bright star named Sirius. If this Earth-like planet orbits with a semimajor axis of 1 AU and an orbital period of 7 months, what is the mass of Sirius?

A) 3 M _$\odot$
B) 12 M _$\odot$
C) 8 M _$\odot$
D) 5 M _$\odot$
E) 17 M _$\odot$