Answer:
Plants. Some Bacteria. Algae. These 3 are the photosynthetic autotrophs..
Why the others don't fit:
Athropods are hetertrophs. Not all bacteria are autotrophs. Only some protists are autotrophs.
Answer:
Carbohydrates give you energy for instance marathon runners will eat a lot of carbs like pasta and bread to give them energy
Explanation:
A way to measure plant growth. The issue with an experiment like this, is there is no way of telling if the plant would have grown differently if you had not added the extra fertilizers. To properly test this you must have "control" plants that would grow in the same conditions just without any fertilizer. You have to have multiple plants as subjects to get a good amount of data and then take the averages of each fertilizer and compare them that way.
(Just as a headsup if you are going to do this as a science fair project, don't use raw egg or unprocessed chicken poop. The egg turns the soil into rock and the chicken feces smells horrible and starts to mold. >< )