Most widely used compound as a source of ethylene is

$CH_2 = CH_2$ is mainly responsible for

What is the influence of ethylene on plants?

$PGR$ which was discovered by Cousins .........

Select the correct option for Ethephon.

$I.$ 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.