Which of the following contains a covalent coordinate bond? (Hint: Estimate the number of covalent bonds that the central atom should form.) 
i. ZnF₂
ii. Al₂Cl₆
iii. CO

• A. i
• B. ii
• C. iii
• D. i and ii
• E. ii and iii
• F. None of the above

Answer: (E)