The production of x-radiation that occurs in an x-ray tube requires the movement of negatively charged particlestraveling from one side of the tube to the other. this movement of charges must occur in: a. vaccuum. b. a tungsten gas environment. c. an aqueous medium. d. any condition that exists inside the x-ray tube, including a nonvacuum.

A

Explanation: In order to generate X ray we need to strongly accelerate the electrons to do that it is necessary a vacuum tube. It applied a high voltage difference to obtain huge kinetic energy to the electrons before impacting to a catode in the other side. The strng electron colision  produces a hard  Xray radiation of bremsstrahlung .  In the X ray spectrum there are also characteristic emission lines from each target. The target to impact the electrons can be tungsten, copper, molibdeno etc. In order to keep high speed of the electron before the colision to the target  we need to conduct this process under vacuum conditions.

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.