Radon is a gas at the temperatures we live in.
The gas is slightly radioactive, and it's soluble in water.
It's a widespread source of natural groundwater pollution,
and is responsible for the elevated level of radiation that's
often measured in the basements of homes.
Answer: Receiver, Geometric configuration, accuracy.
Explanation:
I don't know about hard to make, but it's impossible to make a mechanical wave transmit energy through a vacuum.
Hi. The answer is, "gram". Hope this helps.
Take care,
Diana