Why can plants be more widely spaced in dry thorny vegetation?

Due to low water availability

Dry thorny vegetation develops where rainfall is low and water is not available for long periods. In such conditions, plants must compete for limited soil moisture. If many plants grew very close together, each would receive less water, so plants are often scattered rather than forming a dense cover. Thorny plants may also have small leaves, spines or other features that reduce water loss, but spacing mainly reflects limited water supply.

Option A is correct because low water availability can produce sparse plant growth and wider gaps between plants. Heavy snowfall, tidal water and marshy soil describe very different environments and do not explain typical dry thorn vegetation. The important reasoning link is: low rainfall leads to less available moisture, less dense growth and greater spacing. Thus the answer is based on the ecological pressure of drought.

This is a Class 9 Geography question. Chapter: Natural Vegetation and Wildlife. Topic: Types of Vegetation.