下面这段话看得不太明白，请帮解释一下： Checks drawn from a U.S. bank may be used for margin deposits. Certified, Cashier's or Official checks can be obtained from banks other than U.S. banks. The funds for all checks have to be in U.S. Dollars. International checks (checks drawn from a non-U.S. bank) are currently not accepted. Certified, Cashier's or Official checks 和 International checks有什么区别，为什么后者它不接受？