华氏位片中显示最佳的结构是
A．筛窦
B．上颌窦
C．蝶窦
D．鼻骨
E．下颌骨
参考答案：B
解析：记忆题。
It's easy ______ English and it's important ______.[ ]
A．study, use
B．to learn, to practice
C．speak, say
D．say, speak
日本全面侵华战争发动是从华北事变开始的。
