某DNA分子含有某种限制酶一个识别序列，用这种限制酶切割该DNA分子，可能形出的两个DNA片段是[ ]
CD
Tom’s teacher and friend ____ Mr. Smith.
A．are
B．is
C．arebeing
D．has
I ______ say he ______ speak to her in public at that time, for he was such a shy boy.
A．dare; dares
B．dare; didn’t dare to
C．dared; dared
D．dared; dared not to
