The correct options are
A Total number of trees is 31
C Least common range of height is 85-90 feet
If we add the frequencies of all the bars, total number of trees=3+3+8+10+5+2=31
The highest bar belongs to the range of 75-80 feet. So, the most common range of height is 75-80 feet.
The shortest bar belongs to the range of 85-90 feet. So, the least common range of height is 85-90 feet.