Hi there!
Although there are only 20 amino acids, these amino acids can combine into an innumerable amount of combinations to form different and unique proteins.
In case that doesn't make sense to you, I'll provide you with an analogy. You could be provided with 20 different LEGO bricks to work with. While there may only be 20 bricks, these bricks can combine into a vast amount of different formations, structures, etc. Amino Acids work in the same way.
I would say B because c and d would decrease competition and a would do the same, or just kill the ecosystem.
Hope this helps and don't forget to hit that heart :)
I believe sam's response is correct.
When human is riding a moving target with constant speed over a period of time, we tend to have a visual acceleration perception due to our optical movement.
This make people such as Carrie believes that the carousel horses are accelerating while it actually stayed at constant pace.
A Anything that has mass and takes up space
