A is correct. We know that water buildup is essential for plants (and all other organisms) that live in the desert due to its lack of moisture. So, the question is simply asking which adaptation will help a plant retain the most water in the desert. Here’s what makes each wrong or right:
A. Stem that stores water - Having stems that can retain a lot of moisture and water is absolutely necessary for plants that live in hot and dry biomes. The brief periods of rain in the desert make it easier for plants with water-storing stems to absorb the water and remain hydrated throughout their time. This is referred to as succulence, and most (if not all) plants in the desert are succulents. This is the correct answer!
B. Shallow root system - Many plants that live in deserts tend to have shallow root systems that allow them to quickly absorb and moisture in the environment — and because water never goes too far in the desert, they soak most of it up. Although this is helpful, it is better for plants that live in places with a lot of soil.
C. Large surface area - Having a large surface area is more useful for photosynthesis and may result in dehydration. This is wrong!
D. Flat broad leaves - Again, this adaptation is more favorable for plants that do not live in the desert because, as we know, photosynthesis requires water.
