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.