In a randomized, controlled, double-blind study: select one:

a. experimental subjects are blind-folded when given the experimental treatment.
b. individuals will be assigned to an experimental or control group depending on whether they took part in a pilot study.
c. all experimental variables are held constant.
d. neither the experimenter nor the subject know whether the subject is in a control group or an experimental group.
e. all of the above.

d

Explanation:

In a randomized, controlled, double-blind study neither the experimenter nor the subject know whether the subject is in a control group or an experimental group.

Randomized double-blind placebo control (RDBPC) trials are considered the epidemiological research of  "gold standard." The best analogy is placebo management, which requires blindness of subjects, researchers and test workers. Trial's advantage over an observational study is its the ability to convey causality.

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.

idk and i also need to know where are those bio brainy acts lol