Water covers over two- thirds of earth's surface. yet water shortages are a major problem for many people around the world. why do you think this is the case?

Nowadays many people around the world have problems with the shortage of drinking water. This is due on the one hand to the greater demand for this resource. On the other hand, climate change has resulted in a shortage of rain in some regions of the world. Another serious problem is that we are contaminating fresh water sources. It is expected that by 2025 3,000 million people will not have access to drinking water

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: