Read the following passage and circle the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbers blanks.
There are several types of pollution. However, ___(1)___ is the most serious in our area. It is caused by several factors. Firstly, families dump sewage into the river. Secondly, there are two new factories in our area, and they are dumping chemical waste into the lake and river. Thirdly, pesticides are another source of pollution. Farmers in our area usually use these to kill insects. We do not ___(2)___ enough fresh water to water the plants and crops. People cannot ___(3)___ in the river and the lake ___(4)___ the water there is so polluted. Another negative effect is that sometimes in the afternoon there is bad smell from the polluted river, so people do not enjoy ___(5)___ along it anymore.