A、A merchant doesn’t know the balance before completing a sale. B、No security system has yet been devised for personal checks. C

W: Did you hear about Mr. William’s case last week?
M: Yes. It’s too terrible. As a matter of fact, he should not issue an open cheque in favor of a third party. Anyone who holds it would present it to the paying bank and obtain cash against it.
Q: What happened to Mr. Williams?

W: With the convenience of bankcards, more and more people prefer bankcards to personal checks.
M: I agree. People like bankcards because they offer greater safety and convenience than personal checks.
Q: What can be inferred from the conversation?