Now, to make something clear, not all teenagers make "poor decisions"; the human mind is so complex and multi-variabled that making a blanket statement for every human being is going too far into assumption. But, it is true that in many cases, the brain's development during teenage years does impact its behavior, in fact this sort of behavior can go back as far as toddlerhood. To put it simply, the brain--usually during teenage development when testosterone or estrogen levels are higher-- undergoes a drastic change where testing and questioning the bounds of one's liberty, privilege, traditional ideas, etc. comes into play. This is probably why even today, some groups of people considerer children far below the age 18--the legal age to vote in America-- adult and ready to marry off. They see that a child of that age has begun to adapt to their surroundings and test the bounds of their traditional ideas, and thus see it fit to give them full freedom. Teenagehood is a time when one makes poor, questionable decisions and hopefully learns from them, a time when one tests the bounds of personal liberty, and a time when they hopefully find out how the world works. Teenagehood is the brain's transition one of a child to that of an adult.
King Edward is described in a way that shows he is very different from Macbeth. Macbeth has been a bad leader for Scotland and his rule has been bloody and the people are hurting. It is included to show that the way Macbeth is ruling is not a way that is good for the people and will not last. Someone will try to remove him because of his bloody rule.
to sing in the choir is an infinitive. an infinitive is a basic form of a verb doesn't necessarily need a subject like it's understood so the understood subject is there when the phrase is said so "sing in the choir is your basic verb so it's an infinitive
