The blood-brain barrier occurs when the physical structures of the brain prevent blood from intermingling with the extracellular fluid of brain cells. this separation makes it difficult and dangerous to deliver drugs to specific regions of the brain. therefore, further research on how the blood-brain barrier works is needed to allow more effective delivery of drugs. what potential ethical issues may inhibit such research?

Two students are working together on an experiment that measures the effect of different liquid fertilizers on the thickness of plants’ stems. which is most likely to result in the greatest amount of error in their scientific experiment? a. one student measures the plant stem widths by using calipers. the other student measures the widths of the same plant stems again by using a different pair of calipers. b. one student measures the plant stem widths by using calipers. the other student types the measurements as they are taken into a computer spreadsheet. c. one student weighs liquids for the experiment by using a calibrated scale. the other student weighs liquids for the experiment by using a different calibrated scale.