In some forests and parks that contain varieties of flowering trees and shrubs, there are signs that read "Take nothing but pictures; leave nothing but footprints. These signs help people remember that -- A. all animals feed directly on flowering shrubs that may be removed by people.

B. humans can disrupt habitats by removing flowering trees and shrubs

C. the removal of flowering trees and shrubs will increase biodiversity

D. flowering shrubs grow best in state forests and parks

primary succession begins with a bare rock and ends with a forest secondary succession begins after a natural disaster where there is a temporary setback after a forest fire or local destruction, but the surrounding area can fill in

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: