Response to the first question (I don't quite know how to explain the second): (Here's my simple version, just based off of common sense and background knowledge rather than a textbook. Hope it works!)
Gender is determined by the X and Y chromosomes. Females are XX, males are XY. Since there is already a ratio of 3:1 X:Y chromosomes, meaning that there are many more X chromosomes than Y chromosomes, it is more likely for the child to be female, because they are more likely to get two X chromosomes.
B. Carbon
Carbon is often called "The Element of Life" because it's found abundantly in all living and once living things
Nitrifying bacteria convert ammonia to nitrites or nitrates. Ammonia, nitrites, and nitrates are all fixed nitrogen and can be absorbed by plants. Denitrifying bacteria converts nitrates back to nitrogen gas.
