Which of the compounds, C4H10, BaSO4, Zn(CN)2, Al(OH)3, contain an anion with a -1 charge?

Iknow #2 is d. i just need to know why

Mrs. smith ordered a root beer float (vanilla ice cream + root beer). mrs. smith noticed that the three states of matter (solid, liquid, and gas) all existed simultaneously in her root beer float. a. identify each phase of matter in the root beer float. b. describe the particles of all three phases of matter in the root beer float. (how are the particles arranged and moving? ) c. identify one phase change you would see in a root beer float and described what causes this change.

Which statement is best described as a atom