1.i have got something of particular importance to discuss w

1.i have got something of particular importance to discuss with you .Could you spare me a few minutes?为什么是to discuss?2.there being no spare parts ,the machine is still left unrepaired.为什么是being 不能是to be,been 3.she could do nothing but wait fot the doctor at that time.为什么是wait不是to wait ,waiting,to waiting 4.No passenger is allowed to stick his heas out of the window lest __a.he is hurt b.he would be hurt c.he may be hurt d.he be hurt