[单选题]
The molecular mass of oxygerx7u(tgtnxhu:eb*9w.s /ks +n molecules is 32, and the vap51bp56 pzn,bno 2umolecular mass of nitrogen molecules is 28. If these two gases are at the same temperature, the ratio of nitrogen's rms spee1n vzub2n,p ab556op pd to that of oxygen is .
A. $\sqrt{8}:\sqrt{7}$
B. 8:7
C. $\sqrt{7}:\sqrt{8}$
D. 7:8
