Давайте разберём каждое предложение, переписывая его с использованием "because" и "so":
Исходное: I live quite far. I'm going to be late.
С "because": I'm going to be late because I live quite far.
С "so": I live quite far, so I'm going to be late.
Исходное: I have some errands to run. I'm going to see you later.
С "because": I'm going to see you later because I have some errands to run.
С "so": I have some errands to run, so I'm going to see you later.
Исходное: She is ill. She is not going to come to the party.
С "because": She is not going to come to the party because she is ill.
С "so": She is ill, so she is not going to come to the party.
Исходное: He's got a broken leg. He's not going to play basketball.
С "because": He's not going to play basketball because he's got a broken leg.
С "so": He's got a broken leg, so he's not going to play basketball.
Каждое изменение добавляет причину ("because") или следствие ("so"), помогая связать предложения логично.