Not my teacher giving a shoutout

Which of the following is a common response to cell signaling?

Which statement describes compounds a. compounds are made of one type of atom. b. compounds cannot be represented by models. c. compounds are represented by chemical formulas. d. compounds cannot be broken down into simpler forms.

Which of the following happened during the precambrian era? the first prokaryotic cells the first eukaryotic cells development of photosynthesis all of the above