Perhaps you need the source code and don't have it (as may be the case with a commercialclass library). Or maybe any change would require modifying lots of existing subclasses.
可能需要源代码，而你却不能得到它或者任何的改变需要改变很多存在的子类。
2
The results indicated that, along with application of normal fertilizers, application of sludge organic fertilizer could significantly increase potato yield, commercialclass and quality.
结果表明，在施化肥的基础上，施用污泥有机肥可显著提高马铃薯产量、等级和品质；
3
What this does is it increases the role of this commercial middle class.