Some plants can grow from both a a) seed & cutting b) seed & spore c) spore & cutting

The answer is c. spore and cutting.  Not every plant grows from a seed. Some plants, like ferns and mosses, grow from spores.  Spore is a tiny, one-celled, reproductive unit capable of giving rise to a new individual without sexual fusion. Other plants use asexual vegetative reproduction and grow new plants from rhizomes or  tubers. Techniques like grafting or take cuttings to make new plants can also be used.

A- a reduction in biodiversity