麻烦看看这题-----,we went swimming in the river.

分词短语作状语,其逻辑主语应该和句子的主语一致.
Feeling very hot,he took all his clothes.
这句话中,feeling very hot 的逻辑主语是he.将分词短语转换成一个句子就看得更清楚了：
He felt very hot.（he 是主语）
所以说,选项D是错误的,因为being a very hot day的逻辑主语不可能是we,试着用we作逻辑主语转换一下：we were a very hot day.(是不是很可笑?）
选项B之所以不对,是因为it was a very hot day 是一个完整的句子,we went swimming in the river.也是个完整的句子.两个句子放在一起,中间用逗号,就成了并列分句.但现代英语中两个并列分句之间必须有连词,否则就不规范了（这一点和汉语不一样,是学生们经常犯的一个错误,也是考试中经常考到的一个考点,切记!）.当然,如果在we went swimming in the river前有个并列连词and,那就可以选B了.
选项C和选项B是同样的问题,也是缺少连词.
选项a是独立主格,即带有自己的逻辑主语的短语.这样独立主格不受主语一致要求的限制.