Most common inorganic anion in insect blood

Answer: Option A

Most common inorganic anion in insect blood is Chloride.
Insect "blood" generally does not carry hemoglobin, although hemoglobin may be present in the tracheal system instead and play some role in respiration.
Hemolymph is composed of water, inorganic salts, and organic compounds (mostly carbohydrates, proteins and lipids). The inorganic salts are present in anion and cation form, one of the anions is chloride.