When carbon dioxide comes inside the leaves from their stomata then water and carbon dioxide combine and form a six-carbon compound having six oxygen and twelve hydrogen compound as well. This process is called photosynthesis. The glucose formed in this process is used by plant and animal too. So this process is necessary for life on this earth.
The answer is option C. Number of double covalent bonds between carbon atoms is responsible for causing different shapes of saturated and unsaturated fatty acids. The double covalent bond causes kink in the unsaturated fatty acids because of which their stacking is disrupted and they become loosely packed. The problem with double covalent bond is that unlike single covalent bond it can't rotate and has almost cis-configuration. This is also the reason behind their liquidity at room temperature.
