Molecular orbitals formation involved in the combination of same type atomic orbitals which also have same symmetry for diatomic molecules. So the correct combinations to the formation of molecular orbitals are,

1s + 1s > Ï1s + Ï*1s

2s + 2s > Ï2s + Ï*2s

2pz + 2pz > Ï2pz + Ï*2pz

2py + 2py > Ï2py + Ï*2py

2px + 2px > Ï2px + Ï*2px

2py + 2py > Ï2py + Ï*2py

2px + 2px > Ï2px + Ï*2px

Explanation:

Molecular orbitals are constructed from atomic orbitals by linear combination of atomic orbitals. The 1s, 2s and 2pz orbitals overlap in an end to end manner hence they only form sigma bonding and anti bonding orbitals. The 2px and 2py orbitals overlap side by side and form pi bonding and anti bonding orbitals. Hence the answer.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong