诊断营养性巨幼红细胞性贫血的重要依据是
A．血清铁含量的测量B．血清维生素B12测定C．血清叶酸含量测定D．骨髓象检查E．以上均不是
参考答案：D
In English class, our teacher often creates an environment _____ we are given the opportunity to solve problems ourselves.
A．when
B．where
C．which
D．that
连续爆炸是煤尘爆炸的特征，与有无煤尘没有关系。
