A Petroff-Hauser Counting Chamber Is A(n)

A Petroff-Hauser counting chamber is a(n)

A) glass slide containing an etched grid for counting microbes directly using a microscope.
B) apparatus that traps bacterial cells on a membrane filter where they can be counted.
C) device that measures the amount of light that passes through a culture.
D) device used to count numbers of bacterial colonies on a Petri plate.
E) device that counts cells as they interrupt an electrical current.