18. A cistern is to be built of cement. The walls and bottom will be 1 ft. thick. The outer height will be
20 ft. The inner diameter will be 10 ft. To the nearest cubic foot, how much cement will be
needed for the job?

i believe the answer is d.

hope it you! : d

large crystals result from very slow cooling.

evaporation of water: this would produce an evaporite which is a sedimentary rock. like a salt pan in a desert. not possible to have volcanic rocks originate this way.

crystalization in molten earth: slow cooling over time. (hundreds to millions of years)

crystalization at earth's surface: this results in fast cooling. (a few hours to a few months or years)

crystalization from cooling off hot water: that would be a hydrothermal deposit. while associated with volcanics they are not volcanic rocks themselves and usually occur fairly rapidly.