A chemist is conducting an experiment to find an enzyme that speeds up a reaction between Chemical A and Chemical B. The chemist places Chemical A and Chemical B together in a beaker and then times how long it takes for the reaction to occur. Next, the chemist places the same amount of the two chemicals in a second identical beaker. The chemist adds an enzyme and then times how long the reaction takes to occur.

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:

i took a test for bio that had this question and these were the correct answers, not sure if this is any now lol

the nervous system and the muscular system work together.  

sweat reaches the surface of the skin and evaporates into the air.

muscles underneath the skin relax, causing hair on the skin to lay flat.

gang gang . u. h. uhh.

just tell me if u want me to be serious