Answer:
Due to urease activity, bacteria are able to use urea as a sole nitrogen source and produce ammonia, which increases the pH in the proximal environment, causing Ca2+ and CO32- to precipitate as CaCO3.
The correct answer is random fertilization.
Together with crossing over and independent assortment, random fertilization represents the way by which sexually reproduction contributes to genetic variation. <span>Random fertilization refers to the random event of fertilization when there is no way in knowing which sperm will fertilise which egg (64 trillion possible combinations of genes that can occur during fertilization). Any sperm cell from the male can fuse with any egg cell from the female.</span>
A- valve replacement
b- stents
x- heart transplant
