Terracing ?
Selecting the most
efficient crops
Irrigation
?
Cutting fields into steep
hills
Monoculture
?
Controlling the flow of
water to crops
Machinery
?
Replacing animal power
with machine power

Terracing ⇒ Cutting fields into steep hills

Terracing is a method of farming on hills and slopes where fields are made along the slope.

Irrigation ⇒ Controlling the flow of water to crops

Irrigation is the control of water to crops through various means. Irrigation is very important in farming and has enabled farming in very harsh conditions such as deserts.

Monoculture ⇒ Selecting the most efficient crops

As the term implies, monoculture is the farming of one crop so in order to maximise returns, the most efficient crops are chosen.  

Machinery ⇒ Replacing animal power with machine power.

Machinery is the use of machine power such as farm implements in farming as opposed to animals. Machinery has enabled the transition from subsistence farming to commercial farming for a lot of areas.

the correct answer is a

answer; ///relational devaluation;