The areas most likely to have problems with radon in ground water are areas that have high levels of uranium in the underlying rocks.
(The areas most likely to have problems with radon in ground water; are; areas that have high levels of uranium in the underlying rocks) (areas; have; high levels of uranium in the underlying rocks)
The areas most likely to have problems with radon in ground water areas
are have
areas that have high levels of uranium in the underlying rocks
high levels of uranium in the underlying rocks