Which closing is appropriate for a formal business email?
答案解析
Core concept: Writing (format conventions).
Key analysis: 'Sincerely yours,' (D) is standard formal closing. 'Cheers' (A) is informal. 'Best wishes' (B) is semi-formal. 'Yours' (C) is incomplete without modifiers.
Common mistake: Using colloquial expressions in formal contexts.
正确答案：D