I would not call it a sentence comment. It was the weather that spoiled the picnic. Therefore, I would call it a relative clause referring to "weather".
Building Skills for the TOEFL says it is wrong to use such a sentence:
The weather was too hot which spoiled the picnic.
I believe it is correct to say:
The weather was too hot, which spoiled the picnic.
(That is by adding a comma before "which").
My question is: Why do the authors of that book that the use of "which" in this way is wrong?
Another question: The weather = Subject, was = Verb, too hot = Complement. How is the chunk "which spoiled the picnic" parsed? Is it a "Sentence Comment"?
It seems obvious to me that what spoiled the picnic was not simply "the weather", but that "the weather was too hot". Yes, the "which" clause is a comment on the whole sentence.
"I disagree with Mike, which means you have two opinions to choose from."
***** NOT A TEACHER *****
Some of my books say that you should avoid this kind of sentence in formal writing because it is "loose and ambiguous."
But those same books admit this "usage is fairly common."
One expert gives this sentence: "Marcia nodded several times and smiled, which rather surprised me."
The expert explains that "her nodding and smiling rather surprised me."
The expert says that some people might write it this way: "Marcia nodded several times and smiled, a fact which rather surprised me." (My note: As you can see, by adding the word "fact " you are making it clear that "which rather surprised me" refers to "a fact." That expert does NOT think that "a fact" does much to improve that sentence.)
I will now try to write my own example: "Some people are rude to people whom they do not like, which is inexcusable."
"Which is inexcusable" refers to the WHOLE idea of some people being rude to people whom they do not like.
I suggest that in formal writing, you avoid this "loose" type of sentence. Maybe it would be clearer to write something like:
"The hot weather spoiled the picnic." / "The picnic was spoiled by the hot weather."
My authority: Paul Williams (a professor at Cornell University in the United States), Understanding English (1954).
Last edited by TheParser; 21-Feb-2015 at 12:10. Reason: I used the wrong prefix.
Apparently, it's not in your book, but you might hear:
It was too hot, and that spoiled the picnic.
Apparently, they were hoping for it to be cold and rainy.
Thank you for your comments and answers. Apologies for being so late as I was abroad for around a month.
It surprises me that sometimes the books say something but in practice people say something else.
In the above mentioned example, it was strange that the "which" construction is considered incorrect in the TOEFL book (and perhaps other books as it has been indicated).
Anyways, thank you very much. I appreciate the time you have taken to write those explanations.
1. You didn't ask me if I wanted to go.
2. I don't often visit grammar sites, but when I do I sometimes find that I disagree with those people who style themselves as authorities on the English language. It is especially nervy for them to call their suggestions rules. (How do they get to make the rules?)