My questions based on the practice problem (this is not hwk); thanks a bunch !:

B. How do you tell if the residuals have a trend...? I can't seem to understand this the most

D. I understand for the most part since this is pretty distinct (it looks obvious that it is hetero here; however, I am usually confused when the graphs are different... can someone explain briefly how to distinct b/w homoscedastic vs hetero?)

E. It's wrong b/c we found errors, but when does regression looks "fine"? Can someone explain that please.