Which of the Following Is the Most Effective Closing for a Sales

Which of the following is the most effective closing for a sales message?

A) Making this training choice for your employees today may be the smartest business decision you'll ever make. Consider the benefits, and I am sure that you will agree .
B) Because we are confident that you will choose us for your training needs, we will visit you on Friday to finalize your contract.
C) Complete the enclosed interest card and mail it to us at your earliest convenience.
D) If your sales don't increase at least 10 percent after your salespeople complete our "Closing the Deal" training, you get a full refund. Use our toll-free number to call me by August 1 and begin training on September 1.