Answer:
9 g/ml
Explanation:
5 + 3.3 = 8.5
But you should use sig figs.
5 has no tenths, hundredths, and etc.
Therefore the 8.5 rounds up to 9
So the answer is 9.
It is a trial aimed to reduce bias during an experiment. An example would be a sugar pill, something that has no real effect so that the results of the true trial can accurately be compared. Its like a control group.