sed to do 表示过去常常做某事,而现在往往不做了 i used to get up early in the morning when i was still a hight school student. be used to doing 表示习惯于做某事 i am used to eating rice now. be used to do表示...被用来做某事 Pig Stem Cells to Be Used to Grow Human Organs? be动词包括am,is,are以及他们的过去式were,was。