Answer:
because the ovum is made to fertilize only a sperm at a time, once a sperm enters it closes. It then divides to form twins, triplets and so on
A crystals shape is determined by the arrangement of the atoms or molecules inside the crystal.
Answer: An ellipse that is close to being circular.
If you plant your potatoes in late August, while it is still hot, you may still have them in the cooler months after. Cool weather doesn't really harm potatoes, they can still grow then, it is only when it is frosty that potatoes die off. The foliage will die, but the potatoes will remain securely underground until you are ready to dig them out. Additionally, potatoes can be grown indoors so that you can always have them.