Planting many tress can help us to keep the air clean.这里可不可以把to keep换成keep呢?为什么?
可以换。help?sb?to?do?sth和help?sb?do?sth,?意思一致。
help?sb?to?do?sth?和?help?sb?do?sth?在语法上都是对的,所以这里两者都可用。就是帮助某人做某事的意思,还有一个类似意思的是?help?sb?with?sth
问:He told us to keep a secret of the thing
答:B.being discussed详情>>