静定结构
参考答案：
在几何组成上是几何不变、无多余约束的体系，其全部支反力和内力均可由静力平衡条件唯一确定。
美国电视的制式是（）.
A.PAL
B.NTSC
C.SECAM
D.FAT
—Daddy, would you buy me an MP3 player if I do well in the first city-wide examination?
—I _______, I promise.
A．would
B．shall
C．will
D．do
