高中英语，选择题

这个句子的主语是The students，谓语是were standing ，句子的基本意思已经表达完整。是完整主谓结构。所以其他结构都是修饰成分， by the swimming pool 是地点状语，后面要填的那部分是修饰主语The students 的同位语，相当于形容词的作用，所以必须用非谓语形式，所以选择D。
如果C选项改成all of who wear 就对了，这样all of who wear swimming suit 就是一个定语从句修饰The students。

D为现在分词短语做伴随状语。

C中all of whom是一个引导词，后必须跟从句，即The students were all standing by the swimming pool, all of whom were wearing swimming suits. 这样也是对的。

C好像读上去感觉挺对，那是因为were wearing和单个wearing读上去感觉差不多，因此会出现语感的错觉，要警惕类似的命题。

请记住句中如果出现引导词，那么必须跟从句，跟现在分词短语肯定是不对的。

望采纳！

D是现在分词做状语表伴随。

C可以改成非限定性定语从句结构，The students were all standing by the swimming pool， all of

whom wearing swimming suit .逗号不可省略。

改成ALL OF WHO WEARING 不可以，of是介词，介宾搭配，后面不可能跟主语who。

all wearing 和前面的were all standing 对应，C之所以不对是因为all of whom wore 才是正确答案，wore做定语从句的谓语。

C答案缺谓语 改成 all of whom were wearing