Final answer:
The false characteristic among the options given is (D) They are toxic in high doses because nitrates and nitrites only become toxic at very high levels, not commonly encountered through normal exposure.
Step-by-step explanation:
The characteristic of nitrates that is NOT true is (D) They are toxic in high doses. While nitrates can be harmful at extremely high levels, the options listed as (A), (B), and (C) are accurate descriptions: nitrates are water-soluble, they are found in plants and vegetables, and they can be converted to nitrites in the body. Many salts formed from nitrates are known for their high solubility in water, and the human body has a process known as nitrification by bacteria which converts nitrates to nitrites. However, it is worth mentioning that both nitrates and nitrites can become toxic at high concentrations, but this is typically much higher than one would encounter through a normal diet or environmental exposure.
Nitrates have several characteristics, but one of them is NOT that they are toxic in high doses. Nitrates (NO₃⁻) are water-soluble, which means they dissolve in water. They are also found in plants and vegetables, and can be converted to nitrites (NO₂⁻) in the body. However, unlike nitrites, nitrates are not toxic in high doses.