Using the valence bond treatment suggest the possible trial wave functions for the two lowest energy states of H₂ molecule.
a) σ₁s²σ₁s²
b) σ₁s²σ₁s¹σ₂s²
c) σ₁s²σ₁s¹π₂p⁴
d) σ₁s²σ₁s²π₂p⁴