国内信用证能有效缓解国内贸易中供求双方的资金需求，降低信息不对称，控制业务风险，具有保证付款、资金融通、保障交易安全的基本作用。（）
参考答案：对
The children, ______ had played the whole day long, were worn out.
A．all of what
B．all of which
C．all of them
D．all of whom
隐形眼镜按材料可分为哪几类？
