Why and when should we omit propositions? On a regular basis, I meet with sentences in which the propositions are omitted, like the following. " How to read a thousand word a minute?" Why the "in" before " a minute" should be left out? Why and when should we omit propositions? Thanks for every answer.Thanks! Marie-Hélène. It's my mistake. I do mean "prepositions".

"No students" Vs "No student" Guys,Another question, What's the difference between the following sayings: No students are to leave without the permission of the police. No student is to leave without the permission of the pollice. Sometimes, we say " no students ", and in other cases ,we say" no student". What's the rule? Thanks!

Confused by past tense and past perfect tense. I am often confused by past tense and past perfect tense, especially with the next text: In another chest, which contained the belongings of a ship's officer, there was an unfinished letter which had been written on March 14th, 1943. The captain learnt from the letter that the name of the lost ship was the Karen. The most valuable find of all was the ship's log book, parts of which it was still possible to read. From this the captain was able to piece together all the information that had come to light. The Karen had been sailing in a convoy to Russia when she was torpedoed by an enemy submarine. (quoted from 'New Concept English', book 3, Lesson 32) Can I just say: in another chest, there was a letter which was written on March 14th,1943…… The Karen was sailing in a convoy to Russia when she was torpedoed by an enemy submarine. Are there any distinctions between the two expressions? How can I grasp the useage of past tense and past perfect tense? Thanks! Everyone.

Both nouns and adjectives can be used as an attributive. What's the difference? a noun can be used before another noun as a attributive, so does a adjective. What's the difference ? Is there anything deverse between "a gold watch" and "a golden watch"? Thanks,guys.

what the diffenerace among at, in, on when they are used before a location? Thanks for every answer!