Answer: A. Market Period.
B. Long Run
C. Short Run
Step-by-step explanation:
A.Output and the number of firms are fixed
The MARKET PERIOD is a very short period that refers to a situation where all resources are FIXED. This means that Output itself is fixed and therefore cannot adjust to demand.
B.Plant capacity is flexible. Firms can enter and exit an industry.
This is the LONG RUN. A time where all resources are Variable. This means that factors such as Plant Capacity which is FIXED in the Short Run will simply be Variable and hence flexible in the long run. Other Firms are also free to enter or leave the Industry during this time.
C.Plant capacity and the number of firms are fixed. Firms can employ more labor if needed
This refers to the SHORT RUN which is a situation where AT LEAST one resource is FIXED and others are VARIABLE. As long as there is a Fixed Resource with some Variable Resources, it is the Short Run. Plant Capacity and Number of Firms are fixed but Labor is Variable. This makes this scenario a Short Run Scenario.