Ignorance is obstacle _ progress.

Correct Answer: (A) to Preposition collocations — specifically "obstacle to" — are frequently tested in NTRCA exams. "Obstacle to" — The Fixed Collocation: — "Obstacle" always collocates with the preposition "to" — Structure: obstacle + to + noun/gerund — Examples: → "Ignorance is an obstacle to progress." → "Poverty is a major obstacle to education." → "Fear can be an obstacle to success." Why "to" is correct: — "Obstacle to" means "something that stands in the way of" or "prevents something" — The preposition "to" indicates direction/relation toward something — Similarly: "barrier to," "hindrance to," "impediment to" Why others are wrong: ✗ "obstacle for" — not standard collocation ✗ "obstacle with" — incorrect collocation