noxious: harmful or injurious to health or physical well-being is denotative meaning. Option B is the correct one.
To denote means to represent. This refers to an objective meaning of the word. Noxious means poisonous. The meaning harmful or injurious to health or physical well-being is synonymous with poisonous. For example, smoking is noxious.
To connote means to add feelings or subjective interpretation to a word. For example, " The noxious look on her face made us feel uncertain."