生活和生产中有许多不同类型的杠杆。如图所示的缝纫机踏脚板属于       杠杆，铡刀属于        杠杆。

Homely Hotels has a customer loyalty program in which for every four nights a customer spends at a Homely Hotel, he or she receives a coupon good for one free night at any Homely Hotel. Recently people have begun selling these coupons on the Internet for less than the cost of a night at a Homely Hotel. This marketing of coupons has resulted in decreased revenue for the Homely Hotel chain.
To discourage this undesirable trade in free-stay coupons, it would be best for Homely Hotels to restrict:（）

A. The number of coupons a customer can receive in one year.

B. Use of the coupons to the specific hotel in which they were issued.

C. The valid dates of the coupons to only the month immediately following the date of issue.

D. Use of the coupons to the recipient or people with the same last name.

E. Use of the coupons to Homely Hotel franchises that charge an equal or lesser nightly rate than the franchise that issued the coupon.