Which type of ecosystem has the greatest variation in temperature from its top to its bottom? A. lake
B. pond
C. ocean
D. estuary

C. ocean

This is the correct option, hope it helped :)

what's the question?

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.

: -)