Manuel Observes Diana Giving Very Good Answers to a Series

Multiple Choice

Manuel observes Diana giving very good answers to a series of questions as she practises for a general knowledge contest.Under which of the following conditions is Manuel most likely to attribute Diana's success to external,unstable causes?

A) if Manuel knows that Diana will be his teammate in the contest
B) if Manuel knows that Diana will be his opponent in the contest
C) if Manuel has had no previous experience with questions of the type that Diana answered
D) if Manuel has had considerable previous experience with questions of the type that Diana answered