13. Below are the geometric isomers of Pt(CN)₂Br₂(H₂O)₂. Which one have an optical isomer? (A)(B)(C)(D)(E)

1. The Nobel Prize in Chemistry in 2022 was awarded to click chemistry, or the azide-alkyne cycloaddition to connect two molecular fragments. For their initial discovery, what metal ion was required as a catalyst for this reaction to proceed at a milder condition? (A) Cu(I) (B) Zn(II) (C) Fe(II) (D) Fe(III) (E) Mo(II)