The short-run in production is the time period when

Step 1: Analyze the question The question asks for the definition of the short run in production theory.

Step 2: Explain the concept In economics, time periods in production are defined by whether the inputs (factors of production) can be changed:

• Short run: a period in which at least one factor is fixed (usually capital, such as land, buildings or heavy machinery), while other factors (such as labour and raw materials) can be varied. Output can be changed only by changing the variable factors. The law of diminishing returns operates here.
• Long run: a period in which all factors are variable. A firm can change its scale of production, build new factories, or adopt new techniques.

Step 3: Evaluate each option

• A. Techniques of production can easily be changed. Wrong. Changing techniques takes time, so this describes the long run.
• B. All factors of production are variable. Wrong. This is the definition of the long run.
• C. At least a factor is fixed while others are variable. Correct. This is the standard definition of the short run.
• D. Variable factors cannot be changed. Wrong. Variable factors can be changed in the short run. It is the fixed factors that cannot.

Step 4: Answer

Step 5: Exam tip Remember: Short run = Some fixed. Long run = Left nothing fixed (all variable). Also, the short run is not a set number of months or years. It depends on the industry. For a bakery it may be weeks, while for an oil refinery it may be years.