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 graphs, total number of trees=3+3+8+10+5+2=31
Hence, option A is correct and D is incorrect.
The highest bar belongs to the range of 75-80 feet.
So, option B is incorrect.
The shortest bar belongs to the range of 85-90 feet.
So, option C is correct.