Question

which of the following substances is an element?
a. water (h₂o)
b. carbon (c)
c. brass (cu + zn)
d. methane (ch₄)

Explanation:

An element is a pure substance made up of only one type of atom. Water ($H_2O$) is a compound of hydrogen and oxygen, brass ($Cu + Zn$) is an alloy (a mixture), methane ($CH_4$) is a compound of carbon and hydrogen. Carbon (C) is an element as it consists of only carbon - atoms.

Answer:

B. carbon (C)