心血管疾病中,引起咯血最常见的原因是
A.肺血管炎
B.肺栓塞
C.高血压病
D.二尖瓣狭窄
E.肺动脉高压
参考答案:D
把抛物线y=-2x2的图象向左平移4个单位,再向上平移3个单位,所得的图象的表达式[ ]
A.y=-2(x+4)2+3
B.y=-2(x-4)2-3
C.y=-2(x+4)2-3
D.y=-2(x-4)2+3
In class, we need practice ___________ English again and again.[ ]
A. speak
B. speaking
C. to speak
D. speaks