The letter he had been looking forward to at last .
A. arrive
B. arrives
C. arriving
D. arrived
网友回答
A. arrive
B. arrives
C. arriving
(答案→)D. arrived
解析： 考查句子结构。此题缺少谓语，he had been looking forward to为定语从句，省略了关系词that/which。句子的主干为：The letter arrived at last.句意：他一直期望的那封信终于到达了。故选D。