some factors of production are variable, while at least one factor of production is fixed. all factors of production are variable. all factors of production can be variable or fixed. all factors of production are fixed.

In the long run, all factors of production are variable.

While, in the short run, some factors of production are variable, while at least one factor of production is fixed.

Explanation:

Variable cost is cost that varies with output. If output is zero, no variable cost would be incurred. An example of variable cost is wages

Fixed cost is cost that does not vary with output. An example of fixed cost is rent

In the long run, all factors of production are variable. While, in the short run, some factors of production are variable, while at least one factor of production is fixed.