Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why ?

Considering x-axis as the internuclear axis which out of the following

1.	Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why ?
Answer» `sigma`-bond is formed between two atoms by the END to end (head-on) overlap of atomic orbitals, hence (1), (2) & (4) form `sigma`-bond. In CASE of (3), if x-axis CONSIDERED as INTERMOLECULAR axis, the `pi`-bond will form due to lateral OVERLAPPING between two `p_(y)` orbitals. Solution :(1) 1s, 1s (2) 1s, `2p_(x)` (3) `2p_(y),2p_(y)` (4) 1s, 2s.