'know of' is used when you have personal. In (2), however, the object of. Can it be used in formal conversation/writing?
You would use the present perfect to express something that happened previously, without specifying the time. Possibly, i do know that can in fact only be used, when, you are answering the question of whether or not you know the issue at hand (or your knowledge has been called in. Alright, well, for example, like on saturdays, y’know, what i liked to do.
Also explain the difference between the two, thanks. Why would you have a problem with this? It's not just you that don't know. Recently one of my friends told me that there is distinct difference between 'know of something' and 'know about something' expressions.
I know how to drive a car. I already know how to turn on the television. What is the correct usage of phrase you don't know what you don't know? Please let me know as soon as you figure it out.
I know (about) this difficulty/problem. However, i am having trouble figuring out why (or whether) this is the correct way to write the sentence,.