Open-pit mining is a kind of
surface mining
subsurface mining
stream dredging
smelting process

Option A.

Explanation:

Open-pit mining is a type of surface mining.

surface mining is a process of mining in which removal of soil and rock overlying the mineral deposit takes place.

Open-pit mining defined as the method in which open pit or borrow is removed first for the extraction of rocks and minerals are extracted from earth  and so it is a type of surface mining.

While in contrast subsurface mining is the method of extraction of minerals and ores from underground.

stream dredging involves removal of accumulated sediment from the bottom of water surface.

Smelting is a process in which heat is applied to the ore to extract base metal.

Hence, the correct option is Surface mining.

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b. lithosphere, asthenosphere, mesosphere   is the answer most likely