Which action causes a chemical change? A. leaves dropping from a tree
B. leaves blowing in the wind
C. leaves being burned in a fire
D. leaves being crushed into pieces

According to theories of how life began, how did early organic molecules begin to separate from the outside world? a: specialized enzymes were required b: chains of amino acids created a barrier c: formation of microspheres or vesicles d: rna catalyzed the formation of membranes