营养不良的预防哪项错误
A．供给足量的蛋白质
B．按时添加辅食
C．积极预防原发病及传染病
D．推迟断奶时间
E．合理安排生活
参考答案：D
对DNA组成成分的分析表明，下列的相关比值其中有一个是可变的，它是[ ]
A．A/T
B．G/C
C．(A+T)/(G+C)
D．(A+G)/(T+C)
Mrs. Black doesn't know if her American friend _____ to Heilongjiang. If he _____ here, she will meet
him at the airport.[ ]
A. will come; comes
B. will come; will come
C. comes; will come
D. comes; comes
