Endangered plant species are conserved through
The correct option is C Gene bank
Gene banks are a type of biorepository which preserves genetic material. For plants it could be freezing cuttings from the plant or stocking the seeds
so that endangered plant species are conserved.
A herbarium is a systematically arranged collection of dried plants.
A gene library contains DNA fragments that represent the entire genome of an organism. DNA fragments however, cannot be used to grow the endangered plant.