骨髓检验对下列哪项不能作出肯定诊断的疾病( )
A．白血病B．巨幼细胞性贫血C．缺铁性贫血D．多发性骨髓瘤E．骨髓纤维化
参考答案：C
A new study found ______ a teacher has anxiety about maths, ______ feeling can influence how his or her female students feel about math．
A．when that; which
B．that when; that
C．that if; which
D．if that; that
有爆炸危险环境、火灾危险性大的环境及其他安全要求高的场所，其配电系统应采用（）系统。
A．TT
B．TN-C
C．TN-S
D．TN-C-S
