General Knowledge Questions

The first step in the refining of petroleum is distillation i.e,  the fractionation of crude oil in atmospheric and vacuum distillation towers.

The first process petroleum refinery is known as distillation. In this process, crude oil is heated and fed into a distillation column. As the temperature of the crude oil in the distillation column rises, the crude oil separates itself into different components, called "fractions." The fractions are then captured separately. Each fraction corresponds to a different type of petroleum product, depending on the temperature at which that fraction boils off the crude oil mixture.

Monoculture is a typical characteristics of Commercial grain farming.

Monoculture is the agricultural practice of producing or growing a single crop, plant, or livestock species, variety, or breed in a field or farming system at a time focussing commercial gains.

Monoculture is widely used in both industrial farming and organic farming and has allowed increased efficiency in planting and harvest.

Polyculture, where more than one crop is grown in the same space at the same time, is the alternative to monoculture.

Water has the maximum density at 4oC. So at this temperature, it sinks down to bottom and stays here. If it cools further, it will become less dense and move up. So while the upper layers can cool enough to form ice, the bottom layers remain as water at  4oC .  

Therefore, (C) is correct.