Part A is because there are many answers that aren't included in there. Don't know the rest, sorry, hope that helped a little bit.
part A is because only two points are on his line, the majority of them are not on or near his line.
part B a better line of best fit would be from (0,2) through (5,7) because that's the line with the most points
part C the actual line has double what Jeff's line had
