Angiosperms and gymnosperms resemble in having

C) Siphonogamy
Siphonogamy refers to the process of fertilization in which pollen tubes grow down to deliver sperm cells to the egg, allowing fertilization to occur. Both angiosperms (flowering plants) and gymnosperms (non-flowering seed plants) exhibit this feature. While their reproductive organs differ, both groups rely on a pollen tube mechanism to ensure fertilization.