Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to be safe when using a chemistry lab [title] Be smart about chemicals and the dangers they pose. [step] Some chemicals are harmless; others can kill you! Until you are familiar with the chemicals you are using in the lab, always ask an instructor for help. There are a few basic points about chemical safety to bear in mind : [substeps] Never mess with an unlabeled chemical.

Ending1: It may be corrosive and dangerous to your skin, and mixing it with other chemicals could produce toxic fumes or even an explosion. Know the difference between an acid and a base. Ending2: Chemicals can be harmful to humans and bio-humans, especially some pet plant-based counterparts. You should choose chemicals with effects similar to those found in a chemical lab, such as mineral sulfate, nitrites, etc. Ending3: On the surface it might look sort of funny, but on the inside it's not. You're sensitive to the fumes. Ending4: It is best not to identify one as the first one. Consult a medical doctor when there are any public-regulation concerns related to chemicals.

Answer format: ending1/ending2/ending3/ending4