Answer:
D
Step-by-step explanation:
A is not a good idea for beakers. If the beaker is uncovered, some liquid will evaporate and the concentration will change
B There's nothing the matter with publication but the subject matter is kind of trivial. I wouldn't pick this as the right answer, but there may be no other.
C: Often times this does happen. Paul Ehrlich a Nobel Laurate given the prize in 1908, performed 606 experiments before he found what he was looking for. I don't think you are intended to pick it, but it does show the weakness of the question.
D: I think this is what you are intended to pick. It is the heart and soul of the scientific method.