A、不受限制
B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1487990612273a573ddd6efe84557bc196fa869fd183bimage8.png">
C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/14879906123127fb015d0c2874226ac5088f8a6ab4759image9.png">
D、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1487990612349cb55a17be5c04d258fa53d24925cbac7image10.png">