The atmosphere in the institute he had newly joined congenial to research.

Answer: Option A

congenial : (of a person) pleasing or liked on account of having qualities or interests that are similar to one's own.
disagreeable : unpleasant.
inconvenient : causing trouble, difficulties, or discomfort.
unpleasant : causing discomfort, unhappiness, or revulsion.
unsuitable : not fitting or appropriate


Antonym of congenial is disagreeable