Answer:
Gigantopithecus could stand on its hind legs, and the known jaws of Gigantopithecus widen towards the rear and proposed that this widening occurred to allow for the housing of a trachea (the ‘windpipe’ that connects the lungs to the mouth opening) when the skull was placed directly in top of the head like a human and not carried forward like a great ape.
The answer is D) desertification and deforestation
To know the answer you can rule out the non-possibilities. A is not correct because farmers use them all the time. B is not correct because water and pesticides can flow downstream and carry and deposit sediment. C is not correct because farmers can flood their own farms. When they plant things and a food comes, all of those plants will die or their roots will detach which lowers the food that can be sold. D is correct because farmers don't farm in the desert or the forest, so it would not be an impact of farming.
Very powerful microscopes were needed before cells could be observed in detail
If a scientist is planning to carry out such an experiment it wouldn't be appropriate to go and test this right ahead without any serious protection. It is always advised that scientists first collect data after they've created their initial hypotheses and read the required literature.