Ratio of carbon fixed (photosynthesis) per unit of water lost (transpiration) is called ( )
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The ratio of dry matter production to the assimilation of a particular nutrient element, usually expressed as grams per gram is called ( )
A relationship of two organisms living together (symbiosis) and one derives its nourishment at the expense of the other is called ( )
The number of individuals of a population the environment can support is ( )
为防止砂型落砂、铸件产生裂纹和缩孔,在铸件各表面的相交处应有( )。
A. 凸台
B. 倒角
C. 铸造圆角