sb look for sth.一句中"for"是介词还是仅仅起构成动词短语的作用.还有,如果一个动词后跟了介词,那么这个动词在句中一定是作为不及物动词吗

look sb sth=look sth for sb .look是双宾结构吗,分别举个例子. look for 是否可以拆成look sb for sth?(search for可以拆成search sb for sth) sth to sb 还是 sth for sb spare sb./sth.for sb./sth. by sth for sb. be sth for sb by sth for sb call sb for sth have sth for sb ask sb for sth plan sth.for sb. buy sth for sb. 1.be long for ; be long to 2.look forward 3.leave sb/sth+doingto do 1 it's important (for sb.)to do sth.2 it's time for sth.3 it's time(for sb.) to do sth.4 it's three metres long/high/wide.5 it takes sb.some time to do sth.6 keep sb dong7 keep/make sth+形容词8 look forward to sth./doing sth.9 make/let sb.(not ) d thank sb for sth/doing sth造句 reward sb with sth for doing sth provide sb with sth,provide sth for buy sb sth=buy sth for