The idea of uniting the two Germanys was seductive.

Answer: Option B

Seductive : tempting and attractive; enticing.
Foolish : lacking good sense or judgement; unwise.
Depressive : causing feelings of severe despondency and dejection.
Unacceptable : not satisfactory or allowable.
Repulsive : arousing intense distaste or disgust.

Antonym of Seductive is Depressive