Which of the following factors can lead to desertification in the presence of natural drought?
a. deforestation
b. sustainable grazing
c. underground mining
d. all of the above

Answer : Option A) Deforestation.

Explanation : Factors related to deforestation can lead to desertification in presence of natural drought.

As natural drought hit area is an area which has low amount of water supply in the land. It is also called as below average precipitation land when drought area is deforested it will lead to desertification. As the plants in the drought area are the reason why their is at least low water is found, if these vegetation is deforested then it will lose its capacity to hold water and the land will be deserted.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.