A、On his card. B、On the goods. C、On a sales slip. D、On the invoice. C对话中男士说道“usually I sign a sales slip”，即他通常在购物单上签字。

W: I wish to cash this cheque from U. S. A. , but the man in the next window told me to bring it here.
M: Oh, yes. This is a personal cheque. We wouldn’t be able to cash it for you until the proceeds are collected from the paying bank.
Q: What does the man mean?

W: How do you pay for your purchases with a credit card?
M: Usually I sign a sales slip in the presence of the seller, and the signature is then compared to the signature on the card.
Q: Where should the man sign when he pays for his goods with a credit card?