题目

The Internet has become part of young people’s life.     64     report shows that 38% of students often use the Internet. Most of them get _   65     (use) information on the Internet    66    use the Internet to help in their studies. But many students don’t use it     67     a good way. Some play games too much, some visit websites    68   shouldn’t look at. So bad things may happen      69     students spend too much time on the Internet. _   70   _ is important for students to use the Internet properly. Now we have a textbook, �已知＝（1，2），＝（－2，3），且k+与－k垂直，则k＝（   ）    A.      B.         C.         D.