溃疡型胃癌的典型声像图特征是()。
A.短轴图像上可见多环"同心圆征"
B."火山口征"
C."腊肠征"
D."假肾征"
E."鱼刺征"
参考答案:B
— Did Peter fix the computer himself?
— He _____, because he doesn't know much about computers. [ ]
A. has it fixed
B. had fixed it
C. had it fixed
D. fixed it
一个原子核进行一次α衰变后成为,然后又进行了一次β衰变,成为,它们的质量数a、c、f及核电荷数b、d、g之间应有的关系是[ ]
A.a = f + 2
B.c = f
C.d = g一1
D.b = g-1