洗氨废水含氨应小于等于（）%。
A.1
B.0.01
C.0.035
D.0.35
参考答案：C
Before a problem can be solved, it must be obvious ______ the problem itself is.
A. what B that C which D why
植物病原细菌、植物病原病毒可从哪些途径侵入寄主？
