A、<img width="101" height="25" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/cfed9fff-d314-45b9-bd3d-0e3ab6db0541.png" />
B、<img width="51" height="24" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/c5011ede-074b-43d9-bf6c-f9491257f9e1.png" />，<img width="56" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/b9212ddd-f344-4dd7-90fa-49441c7ed7ce.png" />
C、<img width="109" height="41" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/ea7d18cc-06f0-4c10-ae32-f9a82e3ce202.png" />
D、<img width="104" height="25" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/74974310-b1de-476c-b352-b20259a44bc6.png" />
查看答案
，则A处约束力大小为（ ）。
题57图