What is apomixis?

The correct option is C Formation of seeds without fertilisation
Some species of Asteraceae and grasses have evolved a special mechanism in which seeds are formed without fertilisation. This mechanism is called apomixis.

It is not a method of sexual reproduction since it doesn’t involve fusion of two different gametes.
Rather apomixis is a method of asexual reproduction that mimics sexual reproduction as seeds are produced both in sexual reproduction and apomixis.

Formation of fruits without seeds is called parthenocarpy. These fruits are formed without fertilisation and hence are seedless.