You _________smoke here! Look at the sign． It says "No smoking"．（ ）
A．needn'tB．mustn'tC．canD．may
Look! The model is walking to us．______ nice dress!（ ）
A．WhatB．What aC．HowD．How a
What were you doing ______ I knocked at the door？
I was sleeping．（ ）
A．unlessB．onceC．whenD．while
Mount Xiaolei is not far away from here，but it will still take us a few hours ______ there by bike．（ ）
A．gettingB．to getC．gotD．get
Hi，Sara．Is this ______ English book？
No．______ is on the desk．（ ）
A．your； MineB．your；MyC．yours；MineD．your；My
It is necessary ______ us to help our friends out when they meet difficulties．（ ）
A．toB．ofC．withD．for