Small amounts of it can be found in many kinds of soil and rock, but most radon is concentrated underground in uranium, phosphate or granite rock.
(Small amounts of it; can be found; L:in many kinds of soil and rock) (most radon; is concentrated; L:underground; L:in uranium, phosphate or granite rock)
Small amounts of it most radon
can be found is concentrated
L:in many kinds of soil and rock
L:underground L:in uranium, phosphate or granite rock