In December 1831 , Somerville joined the Royal Scots Greys regiment of the British Army .
Somerville had joined the Royal Scots Greys regiment of the British Army in December 1831 .
Somerville had joined the Royal Scots Greys regiment of the British Army in December 1831 .
写出该句子的释义版本: In December 1831 , Somerville joined the Royal Scots Greys regiment of the British Army . 输出: