Which halogen is most likely to react?
a. br (bromine)
b. f (fluorine)
c. i (iodine)
d. cl (chlorine)

The correct answer is B. Fluorine is the most reactive among the choices. The choices given belongs to the group of halogens which means salt-producing. These elements reacts with metals to produce salts. The reactivity of these halogens can be predicted using the periodic table. As you go down the group 7 elements, reactivity of these elements decreases.

Answerstudying coal cumbustion as an energy source;

Pretty sure it's d. heterogeneous is separated by physical properties.