Device to discourage self-pollination or increase cross-pollination is
a)	Pollen release and stigma receptivity are not synchronized
b)	Anther and stigma placed at different position
c)	Same height of stamen and stigma
d)	Both (a) and (b)

(d)

Flowering plants have developed many devices to discourage self-pollination. In some species, pollen, releases and stigma receptibility is non-syncronised, i.e., either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen.

In some other species the anther and stigma are placed at the different positions so that the pollen can not come in contact with the stigma of same flower. Both these devices prevent autogamy.

The third device to prevent inbreeding is self-incompatibility. This is genetic a mechanism and prevents self pollination (from same flower or other flower of same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in pistil