问题
选择题
—Susan has bought a large house with a swimming pool.
—It _____ be very expensive. I never dream about it.
A．might
B．must
C．can’t
D．shouldn’t
答案
答案：B
题目分析：句意：Susan买了一个带游泳池的大房子。那一定很贵。我从不敢梦想拥有。表示肯定猜测用must be。故选B。
所示的途径依次表示______育种和______育种。其中后一种育种方式的优越性在______。