可以用if替换whether。

　　(2)doubt作动词，后接宾语从句时：在否定句和疑问句中，后面接that引导的宾语从句；在肯定句中，doubt后面一般接whether或if引导的宾语从句。

(教材P16)Will put down his shopping bag and held out his hand，and the cat came up to rub her head against his knuckles，just as Moxie did.威尔放下购物袋，伸出手，那只猫便跑到他身边，在他的手指间来回蹭起了脑袋，就像莫克西常常做的那样。

　　(1)put down放下；写下；记下；镇压

　　put up 举起；建造；张贴；留宿

　　put off 推迟

　　put away... 把......收起来放好

　　put aside 放到一边；存起来

　　put out 扑灭(大火)

　　put forward 提出

　　①We can put you up for the night.

　　我们可以让你晚上留宿。

　　②The game was put off because of rain.

　　比赛因雨延期。

　　③This vase wasn't wiped out properly before it was put away．这个花瓶没擦干净就收起来了。

　　(2)hold out伸出；维持，坚持；阻止；制止；抱有(希望等)

　　hold back 阻止，抑制，隐瞒；退缩，踌躇

　　hold on 坚持不住，继续；别挂电话，稍等

　　hold on to 抓紧，不放开，坚持，不放弃

　　hold up 举起，支撑；耽搁，延误；阻挡