Scientists wanted to cultivate fish in a closed system. what features should be included to ensure a closed system?
a.) allow incoming water from groundwater wells
b.) allow only one species of fish
c.)prevent precipitation from entering the tanks
d.) remove solid wastes produced from the fish in the tanks

it also supports my hypothesis. if you rest first you can squeeze the clothespin more times. from the data i collected the average of the eight people concluded exercise makes your muscles more fatigued and less able to squeeze the clothespin compared to resting before squeezing.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

yes, because even though a theory has a  lot of evidence to support it, it is not always true