Desertification is a process whereby land degradation in arid, semi-arid, and dry sub humid areas results from climatic variations and human activites.

a. true
b. false

TRUE

Explanation:

Desertification is usually defined as the process by which a productive land is transformed into a desert. This process occurs mainly in the arid, semi-arid as well as in the dry sub-humid areas, where there occurs less amount of rainfall and presence of less or no moisture content in the air.

It is caused by various processes, such as-

Thus, the above-given statement is true.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

c

explanation: