Concept:The correct preposition to use when referring to a specific point or exact location is "
at".
Explanation:The blank requires a preposition to connect the action ("demonstrated") to the specific place ("the Drop Zone").
A "Drop Zone" is a precise, fixed geographical point.
The preposition "
at" is the standard choice for indicating a specific location, point, or small area.
For example, we say "at the corner" or "at the airport".
Thus, "demonstrated at the Drop Zone" is grammatically and logically correct.
We can eliminate the other options by understanding their primary uses:
"
By" indicates the agent performing an action or a deadline (e.g., by the pilot, by noon).
"
In" indicates an enclosed space or a large area (e.g., in the hangar, in the city).
"
With" indicates accompaniment or the instrument used (e.g., with a parachute, with his team).
Since the context demands a fixed location, only "
at" fits the sentence correctly.
Answer:at (Option B)
Complete sentence: System performance was demonstrated at the Drop Zone from an altitude of 5000 m.