Complete the text with suitable prepositions. Nuclear war has become a major threat (a)____ the present world. Various kinds of nuclear weapons have been produced (b)____ past few years (c)____ many countries. This is a new and terrible development in the history (d)____mankind. Very few events can be more frightful than a nuclear war. (e)____ a nuclear war, most of the world's population will be exterminated. There will also be an acute shortage of food (f)____ all the crops and stores will be poisoned (g)____ radiation. If nuclear bombs are dropped (h)____ any area, it will be ruined. To establish peace, people all (i) the world should ralse voice (j)____ the year.