The most probable speed of an oxygen molecule in the gas phase at room temperature is 450 m/s. The root-mean-square speed (urms) is therefore

A. slightly less than 450 m/s.
B. much less than 450 m/s.
C. much greater than 450 m/s.
D. slightly greater than 450 m/s.
E. equal to 450 m/s.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

Compound with sulfer  is bright red 

Sorry i dont understand the question can you rephase it?