The energy of `sigma_(2s)`, is greater than that of `sigma_(1s)^**` orbital because
A. `sigma_(2s)` orbital is bigger than `sigma_(1s)` orbital
B. `sigma_(2s)` orbital is a bonding orbital whereas 6 is an antibonding orbital
C. `sigma_(2s)` orbital has a greater value of n than `sigma_(1s)^**` orbital
D. `sigma_(2s)`-orbital is formed only after `sigma_(1s)^**` orbital is formed