便染性病害
参考答案：
也叫传染性病害，包括竞争性杂菌、真菌性病害、细菌性病害和病毒性病害
Many kinds of books, newspapers and magazines _____ in this library.[ ]
A. are kept
B. is being kept
C. are keeping
D. have kept
□021÷5中，如果商是4位数，那么□里最小可填（ ）。
