Which of the following is true for exine?

a. It is the hard-outer layer of pollen grain

b. Made up of sporopollenin which is the most easily degradable substance.

c.  It exhibits a fascinating array of patterns and designs.

The hard-outer layer called the exine is made up of sporopollenin and the exine exhibits a fascinating array of patterns and designs.

Sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known.