病原真菌根据其侵袭部位以及发病的条件，大体划分为（）三类。
参考答案：浅部真菌、深部真菌和条件致病真菌
The computer ______in the shop yesterday.[ ]
A. was bought
B. was buying
C. bought
D. is bought
计算：（3+a）（1-a）=（ ）。
