根据句子意思，用括号中所给汉语提示或英语单词的适当形式填空。（每空一词）
____ Food          has been a serious problem in China in recent years such as fake milk　powder（劣质奶粉）, Toxic Capsules（问题胶囊）. (safe)
____ These comic books ________ (it) are more or less worth reading.
____ ——Is London the first European city        the Olympic Games?——No, it has been held in many other places in Europe.  (hold)
____ More than one person ________(clean) the classroom at 6 o'clock yesterday.
____ It's said that the price of food in China _____ ( rise ) quickly recently.
____ The fish is_____ ( terrible) bad, why not throw it away?
____ The famous writer always spends as much time as he can       to his fans' e-mails. (reply)
____ The suspect ___________(see) running along the street at that time.
____ _______ ( take ) more exercise and you'll become healthier.
____ Though the hike is far ___________ ( tough), I'll try to finish it.