问题补充：
We were told that when Marx was already , he started to learn Russian.
A. in 1840’s; in his fifties
B. in the 1840’s; his fifties
C. in the 1840’s; in his fifties
D. the 1840’s; in his fifties
答案：
A. in 1840’s; in his fifties
B. in the 1840’s; his fifties
(答案→)C. in the 1840’s; in his fifties
D. the 1840’s; in his fifties
解析：考查固定搭配。In the1840’s表示在19世纪40年代。In one’s fifties在某人五十几岁的时候。考查较多的是定冠词和所有格的形式。句意：我们被告知在19世纪40年代，马克思已经50多岁了，他却开始学习了俄语。故C正确。
