家鹅是由天鹅驯化而来的。( )
参考答案：错
解析： 家鹅由大雁驯化而来。
Mrs White found her husband ________by letters and papers and________ very worried.
A．surrounding ; looked
B．surrounded ; looked
C．surrounding; looking
D．surrounded ; looking
计算机网络系统接地要求小于（）。
A.4Ω
B.10Ω
C.5Ω
D.3Ω
