Why does the border between light and dark on the Moon change location?

What is the chemical name of the compound na2co3? use the list of polyatomic ions and the periodic table to you answer. a. sodium carbon oxide b. sodium carbonate c. sodium(ll) carbonate d. sodium oxalate

Quickly what are the following of organisms that existed over a wide area but only for a limited time period called a.soft fossils b.mold fossils c.index fossils d.trace fossils

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium