76. According to the Swedish scientists, the pesticides in rain ____.

1. exceed those in crop sprays
2. can be traced back to crop sprays
3. are not as toxic as they used to be
4. are nothing but atrazine and alachlor

77. Muller and Bucheli found that 2,4-dinitrophenol ____.

1. is widely used in agriculture
2. exceeded atrazine in the rain samples
3. can be measured in the units of nanograms
4. was far in excess of limit in drinking water

78. Scientists used to hypothesize that ____.

1. groundwater was safe for drinking water
2. herbicides and pesticides were harmless
3. pesticides contaminated groundwater exclusively
4. rain would minimize the pollution of drinking water

79. Muller warns us not ____.

1. to tap groundwater for drinking water
2. to use such roofing materials as bitumen sheets
3. to let the first flush of rain recharge underground water
4. to divert the first flush of rain into sewers without removing its herbicides and pesticides

80. Which of the following can be the best title for the passage?

1. Drinking water.
2. Rainwater and Underground Water.
3. Agriculture and Pesticides.
4. Falling Pesticides.

(Reference keys.)