some languages are more difficult to learn than others russi

some languages are more difficult to learn than others russian ____
A such as B for example Cas well Dand so on

能放在最后的是
B for example
再问： d为什么不行？
再答： 因为and so on前面的名词必须在句子中做宾语或者介词短语的宾语，例如 They increased their income by raising sheep and so on.他们通过养羊等方式来增加收入。而原句中主句已经不缺少其它成分了，没有后面的russian for example句子也是完整的，所以用for example这个介词短语做补语