could原型是:canHis subtletycouldnot avail him here .他精明机智在这里无济于事了。

Icouldhear them crying out to one another .我听得见他们相互呼应。He was so pressing icouldn't refuse .他这样坚持，我实在难以拒绝。Hecouldfeel the menace of the spreading .他能感到这种膨胀的威胁。Youcouldat least have sent a card .你本来至少可以寄张明信片来吧。

could 的原型是can意思是，能，会，例如：He can speak English.