题干
.
The custom of giving gifts at Christmas can be traced back to the Wise Men _________gifts to the baby Jesus.
The custom of giving gifts at Christmas can be traced back to the Wise Men _________gifts to the baby Jesus.
A：bring
B：brought
C：bringing
D：being brought
答案(点此获取答案解析）
C
，变形得到R=
，关于此式的物理意义，下面说法正确的是( )
