- Grade 11 and 12 Mathematics (Moderator: geoffrey)
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- Grade 11 and 12 Mathematics (Moderator: geoffrey)
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.