Question

which mining methods often require drilling and explosives?
placer and subsurface
surface and placer
subsurface and surface
open - pit and in situ recovery

Explanation:

Surface mining (including open - pit which is a type of surface mining) and subsurface mining often require drilling to access the ore body and explosives to break up the rock. Placer mining involves separating heavy minerals from sediments and usually doesn't need drilling and explosives. In - situ recovery involves dissolving minerals in place and pumping them out, without the need for drilling and explosives in the traditional sense.

Answer:

C. subsurface and surface