About how long does it take the moon to orbit the earth?

Which of the following is not a symptom of desertification? a) decrease in salt content of the soil b) lowering of the water table c) reduced surface water d) increased soil erosion e) loss of native vegetation

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Q: a: in sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins