边材树种的心边材无颜色区别,木材通体颜色均一,如()就属于边材树种。
A.桦木
B.刺槐
C.桤木
D.榉木
参考答案:A, C
He worked hard and achieved what he set out to do, but ________ what he had owned, including his health and his marriage.
A.at the mercy of
B.at the risk of
C.at the cost of
D.at the service of
以下哪项不属于支气管扩张的X线平片表现()
A.继发性肺叶、肺段不张
B.肺纹理出现可见"双轨征"及杵状纹理
C.囊状或蜂窝状阴影,内可见小液面
D.与支气管相通的厚壁空洞,内有液平
E.肺野内片状模糊阴影