Which level of organization describes the tropical savanna

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

Chromosome 17 is made of over million base pairs.

Select the correct location on the image identify the element that humans need to breathe. 2015 er r ights reserved