'guard'和'ward'是一对同源词，都来自古法语。

'Guard' and 'ward' are ___doublets that both originated from Old French.

这位演员在历史剧中穿着一件绣有金线的紧身上衣。

The actor wore a gold-embroidered ___doublet for the historical play.

显微镜的双合透镜可以有效减少色差。

The ___doublet in the microscope helps reduce chromatic aberration effectively.