Hashimoto's disease is an autoimmune disordee that decreases the ability of the thyroid gland to produce t3 and t4. the student is modeling the reaction to increased tsh levels in an individual with untreated hashimoto's disease compares to an individual without hashimoto's disease. which of the following should be used as an independent variable?
tsh level
trh level
t3 level
t4 level

TSH level, because if we are testing the levels of TSH with a person who has Hashimoto's disease and one who does not have Hashimoto's disease.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.