Increases exponentially is your correct answer
The correct answer is B. The safety only prevents you from pulling the trigger, but does not stop the pin from striking the primer. For example, if you drop the firearm, the pin may hit the primer and fire the firearm. It is always responsible to keep the firearm pointed in a safe direction so that if this happens, no consequences come out of it.
C, they didn't know any better
If an object's velocity is steadily increasing it means that the acceleration is constant at a certain value.
Choice A shows an acceleration of zero which would only be true if the object was not moving or if its velocity was not changing.
Choice B gives us a graph showing acceleration increasing over time and is therefore incorrect.
Choice C is correct because the acceleration is constant. Steadily increasing tells us that the acceleration is fixed at a certain value.
Choice D is incorrect an represents a constant negative acceleration. This would be the case if the object was steadily decreasing in velocity.