一对杂合黑豚鼠产仔4只，4只鼠仔的表现型可能是： [ ]
A．三黑一白
B．全部黑色
C．二白二黑
D．以上三种都有可能
答案：D
We are pleased to know that you have planned to come to the Autumn Guangzhou Fair.We wish to discuss with you some other important things if you could come（）your earliest convenience.
A.by
B.on
C.in
D.at
个人计算机简称PC机，这种计算机属于( )。
A．微型计算机
B．小型计算机
C．超级计算机
D．巨型计算机
