The correct option is D friendliness
The word 'rancour' refers to bitterness and resentfulness, especially when long standing.
Option A, rivalry refers to competition in the same field for certain objective or superiority.
Option B, competition refers to striving to gain or win something by defeating or establishing superiority over others.
Option C, friendliness refers to affability.
Option D, suspicion refers to a feeling or thought that something is impossible.
Thus, according to the meaning, the word 'friendliness' is the opposite of the word 'rancour'.