题干
.
Tom_______at least three coffees every day until his doctor told him to limit it to one.
Tom_______at least three coffees every day until his doctor told him to limit it to one.
A：had drunk
B：drank
C：has been drinking
D：has drunk
答案(点此获取答案解析）
B
，变形得到R=
，关于此式的物理意义，下面说法正确的是( )