A negative feedback mechanism works by opposing variations in conditions. This feedback mechanism tries to negate changes to restore the equilibrium of a system. A neutral feedback mechanism supports a change that occurs in the value of a parameter.

the answer is barium and copper bromide

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.

the answer is d.) potassium