The correct option is A Liver
One of the function of liver is to remove the poisonous substances from blood flowed by their detoxification. Kupffer cells are the large fixed phagocytic cells that are attached to the lining of the hepatic sinusoids in liver and serve to remove pathogens and debris that enter through hepatic portal vein at the small intestine. This makes option A correct. Primary function of small intestine is absorption of digested food while pancreas has both endocrine and exocrine functions. Thyroid gland stimulates metabolic rate, growth and development by its hormones. None of these organs are involved in debris removal.