Which of the following is a synthetic auxin?

Avena curvature test is a bioassay for examining the activity of

$A$: $2, 4-D$ is widely used by farmers in agricultural and horticultural practices.
$R$: Flowering in most plants can be initiated by using high concentration of Auxin.

$IAA$ and $IBA$ synthesis requires:

Phototropism in shoots is attributed to

By hormone application,it is possible to obtain seedless fruits. In which of the following is it $NOT$ desirable to obtain seedless fruits?