Answer:
B. A harmful compound can become harmful when its elements are seperated.
Step-by-step explanation:
In the question, common table salt, NaCl was the illustration.
NaCl is a crystalline solid whjch has different benefits like for preservation, add taste to foods etc. NaCl is generally consumed by humans daily and is found readily. This goes to show that NaCl is a harmless compound but the individual elements that is, Soduim and Chlorine gas,
2Na + Cl2 --> NaCl
Soduim metal is a reactive and unstable element with 1 (valence) electron in its outer shell. Hence why the reaction of sodium strips with water is explosive.
Chlorine gas is very poisonous, unstable as well as reactive because of the 7 (valence) electrons in its outermost shell.