a. 2 > The 23rd pair, the sex chromosomes, differ between males and females (females have two copies of the X chromosome, while males have one X and one Y chromosome). In humans, the sex chromosomes comprise one pair of the total of 23 pairs of chromosomes. The other 22 pairs of chromosomes are called autosomes. <em>Chromosomes are thread-like molecules that carry hereditary information (they are made of protein and one molecule of DNA, which contains an organism's genetic instructions).</em>
Reforestation is a process of planting trees in an area so as to conserve the land as future forest. According to the given situation, reforestation is the practice which can be used by the biologists to grow nitrogen fixing plants in an area so as to increase the nutrient concentration of the soil which have been depleted.
