. Compound pollen grains occur in
A: Calotropis or Asclepias
C: Juncus or Cryptostegia
Angiosperms are flowering plants.
More than 56 families of angiosperms have pollen that fails to separate from the tetrads and results in the formation of compound pollen grains.
Examples of such plants are Juncus and Cryptostegia.
Hence the correct answer is C.