IMO: A

Let T be total no. of players
Senior Players = (1/4)T
Non senior players = (3/4)T

Avg. score per player = Total score/no. of players

Statement 1: Avg. score of Senior player = 18 = total score of senior/no.of seniors.
Hence, total score of seniors = 18X(1/4)T
In the same way total score of non seniors = 12X(3/4)T.
Thus total score of team = (9/2)T+9T = (27/2)T

Therefore, Avg. score per player = (27/2)T/T, T will cancel out and the answer is 27/2. SUFFECIENT

Statement 2: Is obviously INSUFFECIENT