What is the name of the functional group that is attached to this hydrocarbon backbone?

ether
alcohol
alkyl halide
carbonyl group

The answer to your question is: Alkyl halide

Explanation:

Ether: is a functional group in which an oxygen is attached to two alkyl or aryl groups.

                   R ---  O --- R'        

Alcohol: is a functional group which has one or more hydroxyl group in its structure.

                  R OH

Alkyl halide: is a group in which one or two hydrogens are replaced by halogens.

                  R --- X      X = halogen

Carbonyl group: is a structure in which one carbon is double-bounded to one oxygen

                       R --- C = O

                                |

                               R'    

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.