sb usually do sth为什么不要加is

sb usually do sth为什么不要加is sb doesn't usually do sth 用sb do sth ...leaving sb sth sb do sth ignoring the fact that usually+adj sb/sth now let sb to do sth 对吗?为什么 为什么没有：hope sb to do sth 为什么没有：hope sb to do sth 为什么Allow sb to do sth,Ask sb to do sth就有to,而Let sb do sth ,Help sb do sth 就不用呢? 为什么动词后有的接sb to do sth 有的接sb do sth? it use for sb to do sth为什么可以it + 动词+ for sb to do sth? take sb do sth make sb do sth make sb.do sth make sb.do sth. hope sb do sth do sth 什么sb Help sb do sth. force sb do sth hleped sb do sth 中的do要是过去式吗?为什么?