What keeps some of the radiation from the sun in the atmosphere?

ozone

Explanation:

The ozone layer keeps the sun’s harmful radiation in the form of ultraviolet light out of the atmosphere thus protecting life on Earth. Harmful UV radiation causes skin cancer, cataracts and skin cancer. Ozone layer has been depleting because of the use of chlorofluoro carbon. But the reduced use of freons has helped the ozone to recovery itself quickly.

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.