Of the four symbolic representations of different matter below, identify which best represents a single element.

What problem would a person have if the nucleic acid in one of his or her cells were damaged?

Zoe is investigating the composition of substance a, an unknown substance. using chemical processes, she analyzes substance a and determines it is composed of sodium, oxygen, and hydrogen atoms in a ratio of 1 : 1 : 1. what is substance a? a. a compound b. an element c. a heterogeneous mixture d. a homogeneous mixture

What layer of the atmosphere is directly above the troposphere?