Please answer the attached question. Please.............. ........

a) Is auxin phytohormone which is used as weedicide.
b) is referring to ethylene. It enhances respiration rate during ripening of fruits. This phenomenon is ‘respiratory climatic’.
c) refers to Gibberalin which promotes flowering in Long day plants evem in non inductive periods.
SO best option is 3) i.e ethylene which is widely used in agriculture for early maturing and ripening of fruits and vegetables.

A and c is for auxin but it is not used as plant growth inhibitor and B is for ethylene so 3rd option is correct