Weightlessness is

Answer: Option A

Weightlessness is the condition in which a body experiences no net force of gravity acting on it.

It does not mean that gravity disappears, but rather that both the body and its surroundings are in a state of free fall under the influence of gravity, creating the sensation of zero weight.

Option B: Incorrect, because weightlessness is not due to decrease of gravity but due to free fall where gravitational pull is not felt.

Option C: Incorrect, because even in a vacuum, gravity acts on bodies (for example, planets and satellites move in vacuum under gravity).

Thus, weightlessness is correctly defined as zero gravity.