Choose the underlined part that needs correction in the following ques . 20. Water from power stations may cause water in rivers and lakes hotter . A from B. stations C. cause D. rivers 21. Researchers haven't found out what has led in the pollution of the river A found B. what C. in pollution 22. At first had difficulty to understand my friends from English - speaking countries A. first B. had to understand D. from

The underlined parts that need correction are the following:

20. C. cause

21. C. in

22. C. to understand

In conclusion. Each sentence has a different kind of error. The correct forms for each sentence are:

20. Water from power stations may make water in rivers and lakes hotter.

21. Researchers haven't found out what has led to the pollution of the river.

22. At first [I] had difficulty understanding my friends from English-speaking countries.

Learn more about prepositions here:

yes, no, maybe, so i honestly don't know best of luck