There ____________ some birds in the tree.[ ]
A. is
B. are
C. be
答案：B
家庭饮用的纯净水，经检验其pH略小于7，这是因为水中溶有 [ ]
A．O2
B．CO2
C．NaCl
D．NaOH
隔日1次的缩写是
A．q．O．d．B．b．i．d．C．q．dD．q．i．d．E．q．h
