Step-by-step explanation:
1a) c since c is the biggest part of the pie chart
1b) 25% as it is close to a quarter
quarter=25%
1c) A=10%
1d) I think Mr.M's class was difficult since 35% of people got decent grades (a and b). As that is a percentage less than half of the class i would consider that as a difficult class.
Hope this helped.