AC motors power limitation
If any motor design parameter such as winding resistance, frequency of supply voltage, magnetic saturation of iron, air gap dimensions, or others is not what is selected for the motor design, the motor may not be capable of providing the design performance. However, changing and one parameter can not usually increase the power capability except to the extent that the parameter had not been optimized for that design.

The question seems rather pointless as stated. If the question is asking which factor limits the power of induction motor designs in comparison to wound-field synchronous motor designs, the answer is probably none of those mentioned.

Upon further consideration:

The question is likely intended to be answered in the context of a specific lecture or textbook. It is difficult if not impossible to answer when separated from that context.