Flowering plants have developed certain outbreeding devices to discourage self-pollination and to encourage cross-pollination. One of the following is not an example of such an outbreeding device.

The correct option is B Cleistogamy
Cleistogamous flowers are intersexual. It is a condition in which flower does not open. In this kind of flower, anthers dehisce inside closed flowers. Cleistogamy ensures self-pollination.

Dichogamy refers to different maturation time of androecium and gynoecium in the same flower. Here, either the pollen can be released before stigma becomes receptives or stigma becomes receptive before the release of pollen.
Herkogamy is the spatial separation of male and female reproductive organs within flowers. It is almost ubiquitous in animal pollinated hermaphroditic plants.
Dicliny refers to the separation of male and female reproductive parts into different flowers. Diclinous plants may either have female and male unisexual flowers on the same individual (monoecy) or on different individuals (dioecy).