Birds and mammals independently evolved four-chamber hearts
I'm guessing changing gravity
I think the answer is c but I looked it up and got this: system or thing used as an example to follow or imitate.
For question 1:
Look at the graph. In the beginning we start out with a feed of 75% wheat and 25% corn. The weight of the pig is 40. Look at the rest of the graph. Each time they lessen the amount of wheat the pigs eat and add more corn, they get heavier. By the end, the pigs are fed a blend of 25% wheat and 75% corn and they weigh 61 pounds. The answer would be C.
Answer:
It is made up of protons and neutrons
