卸荷板上预留的短钢筋插入孔，须在达到设计强度的（）后方可吊运安装。
A.80%
B.75%
C.90%
参考答案：C
In spite of the negative ________, “So Young”, directed by Chinese director Zhaowei, is well-received by the audience and is a real success.
A．reviews
B．previews
C．revisions
D．proposals
SE序列中180°脉冲的作用是（）。
A.使静磁化向量从z轴转向xy平面上作旋进运动，随之失相
B.使静磁化向量从xy平面转向Z轴，随之失相
C.使静磁化向量从x轴转向y轴，随之相位重聚
D.使静磁化向量从y轴转向x轴，随之相位重聚
