1. The problem asks what a batter must mainly do within a quarter of a second according to the text. 2. The options are: A. Visualize their goals. B. Put on special sight-enhancing glasses. C. See the pitch, judge its speed, and decide when to swing. D. See the ball, and measure its speed. 3. The correct answer involves the batter's immediate reaction to the pitch, which includes seeing the pitch, judging its speed, and deciding when to swing. 4. Therefore, the best answer is C. Final answer: C. They must see the pitch, judge its speed, and decide when to swing.