b) One with spiny leaves and a thick stem.
Step-by-step explanation:
- Plants growing in desert face scarcity of water and they need to check transpiration rate.
- To reduce the rate of transpiration the leaves of desert plands are reduced to spines, which resulted in a reduced surface area and negligible number of stomata.
- The Stems of Desert plants are modified to store water to prevent desiccation and hence they are thick and succulent.