Answer:
Although the question is incomplete, missing options are
- In 1997, they reduced their water consumption.
- In 1996, they planted more trees to curb water pollution.
- In 1994, they used only bottled water for drinking purpose.
- In 1995, they complained about foul odor and taste in water.
Correct option: In 1996, they planted more trees to curb water pollution.
Explanation:
Among given options, a clear trend of nitrate level can be seen. Initially, the nitrate level increased in water in first two years (1994 and 1995) and then it decreased significantly.
From the conditions given in the question, the most probable answer is B the plantation effect (phytoremediation). During phytoremediation, plants take up nutrients including nitrate from the water via roots. This nitrogen is then used for the growth and development of plant body mass (e.g. amino acids). As more plants were growing in later years, higher reduction of nitrate was seen. Resultantly, in 1997, the concentration of nitrate was dropped to 7.3 mg/L.
The other options are not correct due to following reasons.
A. There is no information on water consumption in the question
C. There is no information on people's behavior on drinking water lifestyle.
D. Nitrate in the water cannot be smelled or tasted.
