Halogens

a. group 1 elements
b. elements that make up the f -block
c. elements of the s and p-blocks
d. group 17 elements
e. entire set of d-block elements

The answer is directly the group 17 elements. Those are the ones that begin with Fluorine and Chlorine. They head the group of Halogens. Go down to see the next two -- Bromine (Br) and Iodine(I). All four are halogens. Whatever is in column 17 is a halogen.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates