39. Which of the following statements about the complex ion is true? (A) the complex ion contains Co(I) (B) The complex ion exhibits cis and trans geometric isomers, but no optical isomers (C) the complex ion exhibits two geometric isomers (cis and trans) and two optical isomers (D) because en is a strong field ligand, the complex ion is paramagnetic (E) the geometric isomers of the complex ion have identical chemical properties