Identify the index fossil

How has the scientific community addressed the safety of chemicals? a. chemicals are repeatedly tested, even those that have existed for a long time. b. existing chemicals are tested if they have never been tested before. c. chemicals are tested if they are suspected to have caused a problem. d. only new chemicals are tested.

How are elements arranged in a periodic table

Provide a stepwise curved arrow mechanism that fully explains the outcome of the reaction shown below. oh нао* heat он