A-A+ Mr．Smith __ working till he was seventy years 2022-08-06 11:40:19 问答库 阅读 179 次 问题详情 Mr．Smith __ working till he was seventy years old. A．kept up B．kept on C．kept to D．kept out 参考答案 正确答案：Bkeep on doing sth．意为“坚持做某事”。
