Topic sentences and controlling idea 1.The Colorado mountains are the most beautiful in America.\
topic sentence.：Colorado mountains controlling idea：in America
2.The life cycle of a frog has two stages.
topic sentence： The life cycle of the frog controlling idea.：has two stages
topic sentences(in red) and controlling ideas (in green).
1. People can avoid burglaries by taking certain precautions. (The precautions for?
2. There are several advantages to growing up in a small town. (The advantages of?
3. Most US universities require a 550 point TOEFL score for a number of reasons.
(The reasons for?
4. Air pollution in Mexico City is the worst in the world for a number of reasons.
(The causes of? or (The effects of?
5. Fixing a flat tire on a bicycle is easy if you follow these steps. (The steps for?
6. There are several enjoyable ways to travel between the US and Queretaro.
(The ways to? or (The methods of?
7. Animals in danger of becoming extinct come from a wide range of countries.
(The different countries?[parts, kinds, types])
8. Effective leadership requires specific qualities that anyone can develop.
(The qualities (or characteristics or traits) of?
9. Industrial waste poured into Lake Michigan has led to dramatic changes in its ability to support marine life. (The effects of?