Most widely used compound as a source of ethylene is

Which plant growth regulator is responsible for the triple response?

$CH_2 = CH_2$ is mainly responsible for

$I.$ More female flowers in cucumber
$II.$ $\alpha$-amylase production in barley grain
$III.$ Acceleration of fruit ripening in tomato
$IV.$ Delay in sprouting in potato tubers
From the given effects,identify the effects of ethylene and choose the correct option accordingly.

The gaseous plant growth regulator is used in plants to :

The only gaseous plant hormone is . . . . . . .