When should a comma be used between adjectives?

Which of the following is not a fire safety precaution a; start fires with kindling or other fire starters b: check local regulations and conditions before starting a fire c: clear flammable debris away from fire area d: extinguish all burning embers before leaving

Irony is a between what is expected to happen and what actually happened

Oceans produce approximately 80 percent of the oxygen our planet needs to support animal life. pollution that reaches the ocean through dumping, oil leaks, runoff, and other processes interferes with that oxygen production and poses a real threat to the oxygen content in our atmosphere. if the oxygen content decreases, it is likely that carbon dioxide will increase. this could have dramatic consequences for life as we know it. which does this passage indicate causes a decrease of oxygen in the atmosphere?