Câu hỏi:

 Đọc đoạn văn sau và chọn phương án đúng nhất (ứng với A, B, C hoặc D) cho mỗi chỗ trống.

Smart Shoes  Smart shoes that adjust their size throughout the day could soon be available. A prototype has already been produced and a commercial (21).....may be in production within a few years. The shoe contains sensors that constantly check the amount of room left in it. If the foot has become too large, a tiny valve opens and the shoe (22).....slightly. The entire control system is about 5mm square and is located inside the shoe. This radical shoe (23).....a need because the volume of the (24)...... foot can change by as much as 8% during the course of the day. The system is able to learn about the wearer's feet and (25)......up a picture of the size of his or her feet throughout the day. It will allow the shoes to change in size by up to 8% so that they always fit (26)....... They are obviously more comfortable and less likely to cause blisters. From an athlete's point of view, they can help improve (27)......a little, and that is why the first (28).....for the system is likely to be in a sports shoe. Eventually, this system will find a (29)......In many other household items, from beds that automatically change to fit the person sleeping in them, to power tools that (30)......themselves to the user's hand for better grip.

A prototype has already been produced and a commercial (21).....may be in production within a few years.