At some sites, the weather is too cold or the soil is too dense. At such sites, what might the EPA do to the soil to clean it?

a
Use only chemical solutions to clean the contaminants
b
Excavate the soil by digging it out and treat it off site
c
Use drills to mix it with the existing soil while pulling it to the surface where it can be treated
d
Saturate the soil with water to draw the contaminants to the surface