In recent years, people have become concerned over the loss of ultraviolet rays from the sun.
because it protects the earth from damaging
1. Ozone
2. carbon dioxide
3. nitrous oxide

1. Ozone

Explanation:

Ozone is a substance with the chemical formula, O3, found in the stratospheric part of the atmosphere. It functions to prevent the harmful ultraviolet (UV) radiation from the sun from reaching the Earth. However, due to anthropogenic activities i.e. human activities that releases greenhouse gases e.g. CO2, CFC etc. the protective function of the ozone layer is wavering.

Hence, based on this question, people are concerned over the fact that this OZONE layer is depleting, hence, risking the exposure to the harmful radiation from the sun.

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: