The correct option is
C Small and light
The orchis seeds (0.004 gm) are smallest in Angiosperms. These are small, dry and light and can be carried by wind to over 1000 kms. The orchis seeds are microscopic and very numerous, may be in some species over a million per capsule. After ripening, they blow off like dust particles or spores. They lack endosperm and rely upon symbiotic relationships with various fungi to provide them the necessary nutrients to germinate.
So, the correct answer 'small and light'