33. an extrusive igneous rock with a fine grained-texture, low silica content and dark color is a. calcite b. limestone c. basalt d. shale e. schist

C. basalt

Explanation:

Basalt -

It is a type of mafic extrusive  igneous rock which is composed of magnesium and iron lava , is called as a basalt .

Around 90% of the rocks of the Volcanoes are made up of Basalt .

The texture of this Basalt is , finely grained ,  because , the rocks are found by rapid cooling .

The viscosity of Basalt is low , due to its low content in silica .  

c. seafloor spreading occurs.

d. crust becomes molten rock.

e. denser plates slide under lighter plates.