Which of the following is an environmental factor that can cause an infectious disease?

lack of sleep and rest
lack of nutritious diet
lack of exercise
lack of clean water

Lack of clean water

Explanation: An environmental factor that no one else can control is water, water may be contaminated due to the environment itself.  

Lack of clean Water

Explanation: Lack of clean water isn’t controlable within the citizens in the environment. The other options shown are controlable, such as the “lack of exercise” example. It’s our choice if we don’t want to exercise and It’s controlable. As well as the fact that the other options have nothing to do with the environment.

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: