Questions to consider:
1) Which step involves removing waste products to provide buoyancy to support the brain?
2) Where does the excess CSF flow into?
3) What allows CSF to be released into the blood w/o permitting any venous blood to enter the subarachnoid space?
1) Step 4 (flow through subarachnoid space)
2) Excess flows into the arachnoid villi.
3) Pressure allows CSF to be released into the blood w/o entry into the subarachnoid space.