Think of it like this. Horses do a LOT of galloping, which is hard on the feet! Hooves are a physical ADAPTATION, so that the horses won't experience pain on their journeys. They're hard, so that the horses don't feel the ground nearly as much. Now, mountain goats travel over rough terrain, with sharp rocks and steep inclines. Again, it's really easy for them to get hurt strutting around the mountains, so they evolved hard hooves to protect their feet.
For the first question the answer is D. Systemic
For question number 2 the answer is B. Lungs
<span>Take an anticodon, which is simply a three nucleotide base sequence on the tRNA. An anticodon can only carry one amino acid on it, and it has 3 nucleotides. So, take three anticodons, and how many nucleotides do you get? 9! And since an anticodon has 3 nucleotides, and since an anticodon can only have one amino acid riding on it, there must be three anticodons for three amino acids. So, then, a total of 9 nucleotides are needed.
So the answer is 9.</span>