Answer: Decreases.

The correct answer is **A** because the accuracy with which prices reflect fundamental information depends on the costs of obtaining such information and the liquidity available to informed traders. If filling orders becomes very costly, informed trading may no longer be profitable. In such cases, information-motivated traders will not allocate resources to gather and analyze data, nor will they engage in trading. Without their research and associated trading activities, prices would become less informative. This leads to a decrease in the market's informational efficiency. Options **B** and **C** are incorrect because higher trading costs negatively impact informational efficiency by reducing informed trading.

Author: LeetQuiz Editorial Team