In a double-blind experiment, which of the following is true?
a. the subjects are not told the purpose of the experiment.
b. the experiments are conducted in a specially darkened and soundproof room to eliminate the influence of chance environmental variables.
c. the experimenter does not know which subjects are in the treatment group.
d. neither the subjects nor the experimenter know who is in the treatment group.
e. each experimental subject is assigned to exactly two blocks.

Ans. Option (D).

A double-blind experiment can be defined as a scientific experiment, in which test information is masked from both experimenter and subjects or test group, until the result is obtained.

It is performed to get more accurate outcomes that can be otherwise influenced be observer bias or placebo effect.

Thus, the correct answer is option (D).

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explanation:

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only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.