There are many kinds of birds in Australia,and over 140 species of snakes,many of
are extremely dangerous.
A. them
B. which
C. what
D. those
网友回答
A. them
B. which
C. what
D. those
解析： 考查定语从句。依据空格后的are一词可知，若选A、D两项，两分句间则缺少连词；分析可知，句中的over 140 species of snakes是先行词，这是定语从句，排除C项；which在此代指上文提及的140多种蛇。句意为：澳大利亚有许多种鸟和140多种蛇，其中的很多种蛇都极其危险。