Command subjunctive
Bossy verb + That+subject+ bare form of verb：the infinitive（to be，to do）without the to

recommend that.....(should) 原型V.

C，推荐两件事情：recommend that and that；recommend，建议，也是表命令语气的词，后面跟recommend that sb do sth

CE区别：
C中的代词they可以指代states和biologists，引起歧义；Be用原型应该是省略了should的缘故吧，推荐后面是一个虚拟语气

cut sth back=cut back on sth,削减某物，如：to cut back on spending=to cut spending back 削减开支。
本题some states cut back on trout stocking仍然可以把on sth看成是cut的宾语，处于从句的第一层，而不是介宾作状语。

C，remove用的动词原型，如果是表示之前移走了鳟鱼，应该是过去式，这里的原型指向recommend，recommend两件事，用两个that表述。

C，they可以指代states和biologists，引起歧义
状语和主语的区别：鳟鱼在一些国家被移除，ok，因为鳟鱼天生就与地点相关，生物必须生活在某个空间；一些国家移除鳟鱼，ok

cutting back强调动作的过程，recommending cutting back 改成recommending the cutting back

recommend含命令语气的动词，后面+that sb do sth。
D，recommend that some states cut back on trout stocking and even their being removed，从句和动名词并列，错
E，recommending that some states cut back on trout stocking and (that some states) even remove the trout，从句和从句并列，对

C they指代biologists，但biologists不可能移除t， they指代states才是正确的，C前面用的虚拟be没问题，后面they代词的问题

虚拟语气省略should+V原型。mark一下。