Multiple choice The first stable compound of C4 cycle is oxaloacetic acid phospho enol pyruvate ribulose 1,5-diphosphate(RuDP) fructose 1,6 diphosphate phosphoglyceric acid Reveal answer Fill a bubble to check yourself A Correct answer Explanation In C4 plants, phospho enol pyruvate combines with carbon dioxide to form first stable compound oxaloacetic acid.