Answer:
[tex]m=\frac{M}{\sqrt{1-\frac{v^{2} }{c^{2} } } } \\\\\\m{\sqrt{1-\frac{v^{2} }{c^{2} } }=M[/tex]
[tex]\sqrt{1-\frac{v^{2} }{c^{2} }} =\frac{M}{m} \\\\\\1-\frac{v^{2} }{c^{2} }=\frac{M^{2}}{m^{2}} \\\\\\-\frac{v^{2} }{c^{2} }=\frac{M^{2}}{m^{2}} -1\\\\v^{2}=(-c^{2}) (\frac{M^{2}}{m^{2}} -1)\\\\v=\sqrt{(-c^{2}) (\frac{M^{2}}{m^{2}} -1)} =\sqrt{(c^{2})(-1)(\frac{M^{2}}{m^{2}} -1)} =c\sqrt{(-1)(\frac{M^{2}}{m^{2}} -1)} =c\sqrt{1-\frac{M^{2}}{m^{2}}}[/tex]
I would think it's A ¯\_ (ツ)_/¯
