Of the options that you have offered here, the best answer is “focus on maintain quality.” This does not mean that quality is unimportant in time-based strategies. However, it does mean that it is not the main focus. Instead, it is believed that a focus on time will also lead to the creation of a high-quality product.
A time-based strategy is one in which the firm focuses on reducing the amount of time that it takes to perform a certain task. In such a strategy, the firm focuses on reducing the amount of time that is needed for each step of the process of making and selling a product. Of the options that you have mentioned in this question, all are part of this process except for the focus on maintaining quality. A firm that is focusing on reducing its time is not going to be focusing as strongly on maintaining quality. Instead, it will focus on reducing the time needed to plan and design the product, to changeover production facilities, and to deliver the product.
Thus, the best answer to this question is “focus on maintaining quality.”