`1` of `NO_(2)` and `7//8 L` of `O_(2)` at the same temperature and pressure were mixed together. What is the relation between the mases of the two gases in the mixture?
A. `M_(N_2)=3M_(O_2)`
B. `M_(N_2)=8M_(O_2)`
C. `M_(N_2)=M_(O_2)`
D. `M_(N_2)=16M_(O_2)`