【多选题】Marshall Hall's five principles (1831) for animal welfare are:
A.
An experiment should never be performed, if the necessary information could be obtained by observations. No experiment should be performed without a defined, obtainable, objective.
B.
Scientists should be well informed about the work of their predecessors and peers in order to avoid unnecessary repetition of an experiment.
C.
Justifiable experiments should be carried out with the least possible infliction of suffering (often through the use of lower, less sentient animals).
D.
Every experiment should be performed under circumstances that would provide the clearest possible results, thereby diminishing the need for repetition of experiments.