John was a good boy and never____ to his parents. [ ]
A. lies
B. lied
C. lay
D. laid
答案:B
β射线的实质是()。
A、氦核粒子流
B、高速离子流
C、电磁波
D、高速粒子流
重度烫伤的表现是皮肤发红水肿或起水泡。