a. is gaseous

b. is responsible for phototropism

c. induces femaleness in flowers of cucumber

d. is used for killing weeds (dicots)

e. induces flowering in long-day plants

Solution:

a. is gaseous: ethylene

b. is responsible for phototropism: auxin

c. induces femaleness in flowers of cucumber: ethylene

d. is used for killing weeds (dicots): auxins

e. induces flowering in long-day plants: Gibberellin