Two Populations That Were Once Isolated Come in Contact

Two populations that were once isolated come in contact. Which of the following statements about what might happen is false?

A) If hybrids are unfit, reinforcement of prezygotic barriers would be disfavored.
B) If reproductive isolation is not complete, the two populations could interbreed.
C) Hybrids, if fit, could spread through both populations, resulting in gene flow between them.
D) If reproductive isolation had been established, the two populations could not interbreed.
E) Hybrid zones that last for a long time could develop.