1.Coins are too small in size and they are easily be lost.
2.I thought that you had not had meal./ I thought you had had dinner already.
I thought you had had dinner already. I thought you had had 。。。。过去完成时。 用 have had dinner 现在完成怎样。？
我原以为，是过去时。你吃过饭，是过去的过去。 如果是当时说的话，就是“我现在以为”那用现在完成时是完全可以滴 （以上完全是个人观点）