A because Only plant cells have chloroplasts
<span>Because the atmosphere is thinner, there would be less pressure keeping the heart at its current size and it would expand and become too large to work properly</span>
Answer:
Explanation:
It certainly isn't the last one. A theory is close to a guess. It fits all the known facts, but there is usually something missing. If someone figures out what is missing, usually by experiment, then the theory become a fact.
The rest of them (1 2 an 3) can all be true. 3 is the least viable. You have to be able to come up with a counter example to reject a theory.
I'm not sure about 2. New phenomena can still be part of current theories. Reluctantly, I wouldn't choose 2 because
1 is the best answer of a very poor lot. Do not be surprised if you use it, that it turns out to be wrong.
