Why is this the answer?

The answer is peanut because this riddle is a fun and clever word puzzle that perfectly describes the shell and the nuts inside. Let us carefully look at each part of the riddle together to see how it works. The first clue says, "A house with two occupants, sometimes one, rarely three." Think about picking up a peanut that is still in its shell. The shell itself is the "house." It is a nice, cozy, beige home that keeps the tasty peanut nuts safe. The little nuts are the "occupants" or the "boarders" who live inside the house. If you open a lot of peanut shells, you will quickly notice that most of them have two nuts nestled side-by-side inside. That is the "two occupants." Sometimes, a peanut pod does not grow as large and might only have a single nut inside. That is the "sometimes one." And then, if you are very lucky, you might find a big, plump shell with three little nuts all packed together. That is the "rarely three." This first part of the riddle is a perfect, detailed description of what a peanut looks like before you eat it. The second part of the riddle then tells us what to do with this special "house" and its "boarders." It says, "Break the walls, eat the boarders, then throw away me." Since the shell is the "house," the hard outer shell is like the "walls." To get to your snack, you must break or crack those walls open. Once the walls are broken, the "boarders," which are the peanut nuts, are ready to be eaten. We take them out of the house and enjoy the yummy crunch! After we eat the nuts, what do we have left in our hand? The empty, broken shell. Since we do not eat the shell, we simply toss it in the trash. The shell is the part saying, "throw away me." The riddle uses imaginative and tricky words to tell the whole story of opening a peanut and enjoying the delicious prize inside. This fun puzzle makes the peanut the only thing that matches all the clever clues perfectly.