简述预防接种的途径和方法。
参考答案：
（1）皮上划痕。
（2）注射，包括皮下、皮内、肌肉注射。
（3）口服。
（4）喷雾吸入等。
Buses were not able to go normally on the roads because of the heavy snow and more than
one student _____ late for school that morning. [ ]
A. have been
B. has been
C. were
D. was
典型流行性脑脊髓膜炎脑脊液的改变是（）.
A.白细胞增多，蛋白升高，糖含量低
B.白细胞减少，蛋白升高，糖含量高
C.白细胞减少，蛋白正常，糖含量正常
D.白细胞增多，蛋白降低，糖含量高
E.白细胞增多，蛋白升高，糖含量正常
