Which of the Following Processes Is Consistent with the Law $\mathrm{C}$

Multiple Choice

Which of the following processes is consistent with the law of conservation of four-momentum? (Answer $\mathrm{C}$ if it is consistent with the law; $F$ if it violates it.)
-(e) A particle of mass $2 m$ at rest decays to two identical particles each of mass $m$ that move in opposite directions away from the decay position at a speed of 0.5 .

A) C
B) $F$