31. Linda couldn't have broken into the teacher's office at midnight, for it was only nine o'clock ______she returned to the dormitory and had a sound sleep.
34. All of our equipment dates back to the 1960s and 1970s; we cannot make products that compete with foreign products, we can buy the necessary technology.
40. _____ we can take some measures to cut the losses to the minimum.
A . As earthquakes are difficult to predictB . Are as earthquakes difficult to predictC . Difficult are as earthquakes to predictD . Difficult as earthquakes are to predict