某物体的密度ρ与4℃纯水的密度ρ水之（）称为物体的相对密度。
A、和
B、差
C、积
D、比
参考答案：D
The family were enjoying their dinner, so I was wondering if I had arrived at a/an ________ time.[ ]
A. awkward
B. prosperous
C. flexible
D. particular
