A.υ(N2):υ(NH3)=0.6mol•L-1•min-1:1.8mol•L-1•min-1=1:3≠1:2,故A不符合;
B.υ(N2):υ(H3)=0.6mol•L-1•min-1:60×0.045mol•L-1•min-1=1:4.5≠1:3,故B不符合;
C.υ(H2)=0.045mol•L-1•s-1=60×0.045mol•L-1•min-1=2.7mol•L-1•min-1,与υ(H2)=1.2mol•L-1•min-1不相等,故C不符合;
D.υ(H2):υ(NH3)=60×0.045mol•L-1•min-1:1.8mol•L-1•min-1=3:2,等于化学计量数之比,故D符合;
故选D.