Whereas the sense of taste is based on (how many? ) classes of taste receptors, the sense of smell has over (how many? ) different receptors for chemicals associated with odor.

6 classes of taste receptors and 350 different olfactory receptors

Explanation:

There are different tastes which are based on the basic 6 classes of taste receptors such as sweet, salty, sour, bitter, umami and starchy.

While the sense of smell has over 350 olfactory receptors for chemicals associated with odors.

it would be c. xylem.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)