The excretory system the respiratory system by
• introducing more oxygen into the lungs
• circulating blood into and out of the lungs
• removing carbon dioxide that is produced during respiration
• removing urine that is produced during respiration

The correct answer would be "removing carbon dioxide that is produced during respiration".

An excretory system with the help of circulatory system removes the carbon dioxide produced as a result of cellular respiration.

The carbon dioxide produced in a cell is converted to carbonic acid with the help of carbonic anhydrase. The carbonic acid is then transported to the lungs in a dissolved form with the help of the blood.

At the alveolar site, the carbonic acid is converted back to carbon dioxide with the help of same enzyme carbonic anhydrase. The carbon dioxide is then excreted out with the help of the lungs.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

emerging idea only occurs as a raw idea that could appear out of nowhere. meanwhile, to reach scientific consensus , that idea must be structured and tested over and over again through various experiments. the scientific consensus transforms the raw idea into idea that is more reliable through the process of scientific elimination.