Question V. Read the following passage and put a word in the box in each of the numbered blanks: 
fish - threatens - garbage - introduced  - serious

Air pollution is a (1) ________________problem in many cities. Motor vehicles, factories and other sources create so much air pollution that it may hang in the air like dirty fog. Air pollution (2) ________________  the health of the people who live in cities. City wastes cause water pollution when they are poured into the waterways. These wastes kill (3) ________________ and make some areas unfit for swimming. In addition, many large cities have difficulties in disposing of their garbage. The amount of  (4)________________  grows each year, but places to put it are quickly filling up. Citizens, governments, industries, scientists, and business people must work together in different ways to gradually reduce pollution. For example, most cities have (5) ________________ recycling programmes.
___________ 2. ____________  3. ____________  4. ______________ 5._____________