Mitochondria breaks down what kind of molecule to release energy?

the answer is c. it will give up it's valence electron to the other atom.

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.

you can have just about every answer you can think of

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.