运行中的桥梁在检定时，钢材的（）可以提高。A、强度 B、冲击韧性 C、容许应力 D、

使用金刚砂车针进行牙体预备时，使用的力量大小为（）

A.10～30g

B.75～100g

C.60～90g

D.30～60g

E.100～150g

.

A．

B．

C．

D．

The growth of phytoplankton is often limited by the availability of ______.

A．oxygen

B．hydrogen

C．nitrogen

D．carbon dioxide

Which of the following most accurately describes the shapes of the average variable cost (AVC) and average total cost (ATC) curves（）

A. The AVC and ATC curves are both U-shaped.

B. The AVC and ATC curves both decrease initially, and then flatten.

C. The AVC curve is U-shaped whereas the ATC curve declines initially then flattens.

唐诗之中“妾家住横塘”这句，原创作者是谁？