Why are deserts often only sparsely populated?
a. humans do not think deserts are attractive landscapes
b. a lack of rain makes it hard to grow crops or find sources of drinking water
c. the sand and rock of deserts make construction efforts difficult
d. deserts often do not have valuable natural resources like gold or oil

B. a lack of rain makes it hard to grow crops or find sources of drinking water

Explanation:

The deserts are the sparsely populated land and they are due to the deficiency of the rainfalls and the arid and dryness of the lands are a fact of this. The dryness is an attribute to the ruggedness of the lands and the variedness topography the climate of the ace is hot to humid and has warm and experiences extreme temperatures.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.