John (travel) to Russia next week correct the tense​

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

Amap that uses a range of colors and shading to represent the elevation, depth, or landscape of specific features on earth is a/an map.

Air can be considered a mixture. which statement does not explain why?