Answer:
The correct answer is - valid.
Step-by-step explanation:
In this case, there is consistency in the results measures in the experiment which makes this method reliable. The consistency of a measure is referred to the reliability.
It is also given that the level of contamination of individual containers as per the average parameter of the contamination of large containers which makes this method not valid as the measurement method is how correctly it measures the true value of the parameter.
Thus, the correct answer is - method is reliable, but not valid.