Question: What is the one exception to the NFL's 4-preseason-game limit?

Is The league has tacitly forbidden the playing of non-league opponents, with the last interleague game having come in 1972 and the last game against a team other than an NFL team (the all-NFL rookie College All-Stars) was held in 1976. a good answer to this question?

Available choices:
(I) yes;
(II) no;
(II)