Question

which is a concern about mining for uranium?
heated water could be released into the environment.
dust released in the air could be radioactive.
supplies could become low during a drought.
it is too commonly found, and mines could be too plentiful.

Explanation:

Uranium is radioactive. When mining uranium, dust containing uranium particles can be released into the air. Since uranium is radioactive, this dust would also be radioactive, which is a significant environmental and health concern.
Heated water release is more associated with nuclear power plant cooling (not mining). Supplies being low during drought is not a key mining - specific concern for uranium. And uranium is not overly common; it is a relatively rare element.

Answer:

Dust released in the air could be radioactive.