Final answer:
The 'spec' counts dead and live cells, but the numbers may be incorrect in certain phases. Pour and spread plates count live cells only and provide accurate counts. Therefore, the correct option is B.
Step-by-step explanation:
The 'spec' is a method of cell counting that counts both dead and live cells in a culture. However, the numbers obtained from this method may be incorrect if the culture is in the stationary or death phase. On the other hand, pour or spread plates are methods that count only live cells. These methods are used when accurate counts of live cells are required, such as in assessing infections or the effectiveness of antimicrobial compounds.