Place the events in chronological order

3, 4, 2, and 1   (I numbered them 1-4 starting from the top)

Explanation:

First weathering breaks down rocks to form sediment, Then that sediment as well as fossils and bones from animals and plants get added together. Then flowing water adds clay or calcite to the mix, hardening them all together. Finally, after many years the rock has turned into hard solid rock with several types of inorganic and organic materials in it.

(I hope this helps you!)

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: