Recently, we discussed the overuse of prepositions, and how they did not help if you wanted to write concisely. (Some common prepositions are in, of, at, on, for, with, to, between and by.) On the other hand, you must not omit essential prepositions.
Words such as “type” and “couple” always require the preposition of.
What type binding do you require?
I need a couple minutes.
What type of binding do you require?
I need a couple of minutes.
Note: It is not wrong to end a sentence with a preposition today. It all depends on the emphasis and effect you want to achieve.
He wanted to know which project I was involved with.
If I was working on a report and wanted to achieve a formal tone, I would write:
“It is essential to understand to which decision he was referring.”
To write with a more informal tone— in a letter or email — I would write:
“It is essential to understand which decision he was referring to.”
We trust these couple of pointers will help you with your writing.