Balance the equation by inserting coefficients as needed. equation: ZnS + HBr -> ZnBr_{2} + H_{2}S ZnS + HBr ⟶ ZnBr 2 + H 2 S

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