Sporopollenin is one of the most resistant organic material.
True
Exine of pollen grain is made up of sporopollenin. Sporopollenin is a highly resistant organic material which can withstand high temperature, strong acids, alkali, etc. It protects the pollen grains from physical and biological decomposition preventing their natural decay. It is so durable that because of this substance pollen grains are often preserved during fossil formation.