Starting with 12 grams of original atoms of a decaying isotope how many of the parent atoms will remain unchanged after three half-lifes ?​

Which statement is the best summary of the model? a-a series of aerobic and anaerobic reactions take place in cells b- the sun's energy moves through trophic levels in a food chain c-light energy is converted into stored chemical energy plants.d- food molecules are broken down in the cells if living things.