I just wondering whether it means that "what" can never change "which" and can be viewed as "the thing that/which". Am I right?
***** NOT A TEACHER *****
Good morning, Olegv.
(1) It's great that you continue to ask until you understand.
(2) I have read the other posts, and I think I understand the matter better.
(3) I THINK that you want to know why "which" cannot be used for "what" in your sentence. Am I right?
(4) To be honest, maybe the best thing is for some knowledgeable person to explain it in your native language.
(5) I have been thinking about your question a lot. May I offer some ideas?
*****
Let's say you enter Harvard University this year. You graduate in 2014. You then attend other famous universities (Oxford, etc.). During this century, you fill important positions in industry and government. When you are 100 years old, the world's newspapers congratulate you.
*****
One newspaper will write: His entering Harvard in 2010 was the first act in_____.
The blank is filled with a noun clause (object of "in"): What turned out to be a distinguished career.
In other words: His entering Harvard was the first act among many acts that resulted in his having a distinguished career.
I think that you understand and accept this use of "what."
*****
You want to know why the following is NOT equally acceptable:
His entering Harvard in 2010 was the first step in which turned out to be a distinguished career.
(a) Please remember that "which" is a true relative pronoun.
(b) In other words, it is a SUBSTITUTE word for an earlier word (or phrase).
(c) In our sentence, "which" is a substitute for "the first step."
(d) Therefore, if we used "which," then the sentence would read:
His entering Harvard in 2010 was the first step in the first step turned out to be a distinguished career.
As you can see, this does not make sense. It was not his first step that turned out to be a distinguished career. It was a series of steps. In other words, his entering Harvard was merely the first step in WHAT (that which/ something which) turned out to be a distinguished career.
*****
Are you aware that this website has a forum in which you may type your question in your native language, and someone will answer you in your native language?
Have a nice day!
P. S. I used "act" and "step" in the same sense. Hope it didn't confuse you.