What is a substance that cannot be broken down into other substances by chemical reactions?

What best describes lactic acid fermentation?

Nucleic acid certain protein cell membranes certain carbohydrates

Iwill make you brainliest pleeze answer this fast i have to turn it in really soon brainliest promise easy question 6th grade ! a weather map shows a high pressure system with circles around it. what does this mean? a) an occluded front b) areas of equal altitude c) areas of equal pressure d) a stationary front