Why was the geocentric model of the solar system accepted by scientists for many years? Select the two correct answers. A. The model described the solar system correctly.
B. The model accurately predicted the movements of the planets.
C. Suitable technology was not available to disprove the model.
D. Observations with telescopes confirmed the predictions made using the model.

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:

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

c. establishing proper sleep hygiene