Answer & Explanation
B) 40 samples
The plate rotates a distance sufficient to allow the tube, when it next moves down, to dip into the next cup. One complete rotation of the plate thus presents 40 samples. As the sample plate completes a cycle, a switch is operated, which stops the rotating action of the plate and the sampling action of the sample probe. The sampling rate can be adjusted to 20, 40 or 60 per hour.