Where do nearly all of the body's chemical reaction, including those that produce energy and build new tissues, take place?

The right answer is aqueous medium (or water solution).

Because of its ubiquity, water has long been considered an inert liquid simply filling the intermolecular spaces in living organisms. It represents about 65% of the mass of living beings. All constituents of the cell "bathe" in an aqueous environment. It is in this environment that the exchanges between the cells take place, that the reactions of the metabolism take place, etc.

answer: proteins

explanation: complement is   system of circulate in the blood in a inactive form

i believe is what you're looking for?