Choice A: The proverb basically means that on the road to success there are many tempting things that could keep you from being successful such as greed and other things. So say you want to be a lawyer when you grow up, someone you see in public might harass and say rude things to you making you want to fight them. This could be considered a parking space because you getting into an altercation with that person can prevent you from being successful.
Choice B: I agree with it because there are many things that could prevent you from being successful when you are trying to. There are obstacales and many things may get into your way. Take the hercules cartoon movie for example, Hercules was going on a bunch of quests to prove himself to the gods, but then he met meg on the way(this would be considered the "parking space"). This was preventing him from being successful because meg was getting in his way of proving himself to the gods, because he was getting distracted by her.
The novel to kill a mockingbird came at a crucial time in american history in which (segregation) and (racism) were fueling debates across the country.
