What is the definition of a probe? It is a huge structure in space where astronauts live and work.
It is a manned vehicle that allows astronauts to travel into space.
It is a piece of equipment that is designed to orbit Earth in space.
It is a device that collects information from space and sends it back to Earth.

1: a slender medical instrument used especially for exploration (as of a wound or body cavity)

2a

: any of various testing devices or substances: such as

(1): a pointed metal tip for making electrical contact with a circuit element being checked

(2): a usually small object that is inserted into something so as to test conditions at a given point

(3): a device used to penetrate or send back information especially from outer space or a celestial body

(4): a device (such as an ultrasound generator) or a substance (such as radioactively labeled DNA) used to obtain specific information for diagnostic or experimental purposes

b: a pipe on the receiving airplane thrust into the drogue of the delivering airplane in air refueling

the answer is b. the tracer looks harmless in flight, but the pilot’s bitten lips and white knuckles suggest how dangerous it can be.

answer is b,

"the tracer looks harmless in flight, but the pilot’s bitten lips and white knuckles suggest how dangerous it can be."

it was correct.