What causes an echo? refraction

rarefaction

reflection

please help

How many atoms or molecules are there in a mole of a substance?

Na chemical reaction, activation energy increases the of the reactants. this outcome causes the particles to collide, which results in the of new products.

Certain types of organisms such as fireflies and anglerfish can produce light through chemical reactions in a process called bioluminescence. what kind of chemical reactions occur during bioluminescence? o a) exothermic ob) endothermic oc) recomposition od) decomposition