字母表里的第三个字母是c。

The third letter in the alphabet is ___c.

这首歌的主旋律是从中央C开始的。

The main melody of this song starts from ___middle C.

这个古钟上的铭文显示它建造于公元100年（C代表公元100年）。

The inscription on this ancient clock shows it was built in ___C, which means the year 100 AD.

这座城堡建于12世纪。

The castle was built in the 12th ___century.

这幅画创作于1500年。

This painting was created ___in 1500.