I have always get confused by the use of the word 'which' because of its various possible comonations, such as 'in which', 'to which' and 'for which'. In fact, it occurs to me that it can be used together with a wide range of prepositions. I hope you can give me guidelines on how to distinguish between them. Another questiion is that I have been told the word 'which', when it is used for the purpose of giving further details, has to be placed right after the thing that is being described.
For example, in the sentence 'One of the questions in the Physics paper, which is about electromagnetism, is to be canceled as announced by the teacher.' I would like to know whether 'about electromagnetism' appears to a native speaker as describing the questions involved in the paper or the whole set of paper.
Thank you for all your help.
This physics paper's questions will all be concerned with electro-magnetism.