Read the following statements related to auxin
a) Auxin helps to prevent fruit and leaf drops at early stages but promotes the abscission of older mature leaves and fruits.
b) Auxin was first isolated from human urine. 
c) NAA, and 2, 4 – D are natural auxin.
d) Auxins are generally produced by growing apices of stems and roots
e) IAA and IBA have been isolated from plants
How many statements are correct?