My english kind of makes me confused about Japanese.
は means the main focus is the thing after it.
が means the main focus is the thing before it.
This is my understanding about one of their many differences. I wonder if this difference is gone when it comes to the subject of a clause.
Here is what i mean:
The two sentences above both mean "I don't know what it is.", right?
I picked two examples from a Japanese ariticle about English clauses (http://ameblo.jp/cc-no-blog/entry-11132742841.html):
Do you know when your brother will come back？
I know who broke the window.
が is written in the examples. Should I always use が in a clause, or I can use "は" also ?
(Since I have definitely seen は being used in a clause, I would like to know if that is just spoken Japanese or something. Is it appropriate to use it like that in formal writing? )