How has technology changed farming a)pesticides are no longer used on most farms b)farms produce less food then they used to c) farmers use mechanical devices to do many tasks d)there are a few farmers than there used to be

C) farmers use mechanical devices to do many tasks

Explanation:

The tasks that farmers used to do manually like threshing, harvesting etc or with the help of animals like ploughing are now being done by them with the help of mechanical devices. Ploughing which was earlier done with the help of bulls is now done with the help of tractors. People involved in threshing, harvesting etc have now been replaced by  threshers and harvesters. Tractors, threshers, harvesters etc. are mechanical devices which make farming very easy, fast and are also much efficient, as a result of which productivity has increased manyfold.

hydroxyl -oh

alcohols, always polar, can form hydrogen bonds with h2o molecules

carboxyl -cooh  

cargoxylic acids, has acidic properties which is a source of hydrogen ions, found in cells in ionized for with a charge of oh-1

carbonyl > co

ketone if within skeleton, aldehyde if group is at the end of skeleton, k & a may be structural isomers, it determines 2 sugars (ketose & aldose)

amino -nh2

amines, acts as a base, it can pick up h+ ions from surrounding solution, ionized with charge of 1+

methyl ch2

addition to rna/dna affects and gene expression

phosphate -opo3 ²⁻

organic phosphates, contributes to negative charge to, molecule that it is a part of, and potential to react with h20

sulfhydryl -sh

thiols, cross-linking stabilize the protein, and it is structure