You are right that English tends to use "to do" in questions, except for auxiliary verbs. But there seems to be an exception when the interrogative word is part of the subject:
- Who came to see you?
- What caused this change?
- Whose car hit you?
- Which way leads to success?
- How many numbers exist?
This is a question about English, not Czech, so maybe you want to bring it up in an English course. Or maybe an English native speaker will be kind enough to comment here.
Yes, English uses "do" forms in many questions, usually when we are asking about an activity and something or someone related to it, for example, “Do fish swim?” or “Does she have a car?” or “Do they play tennis?” But with "How many numbers exist," we are not really asking about the existence of numbers, but rather about the quantity of numbers that exist, because we already know there are things called “numbers.¨ So while we night ask "DO numbers exist?" we would not normally ask, "How many numbers DO exist?"
Thank you for commenting, I always appreciate your posts, especially since you became a Czech contributor from a Czech learner!
You replied to the OP Zubkov but maybe you had a look at my answer, too. Reading your proposal that “to do” is used to ask about the existence of something I searched the WWW but could not find a serious article about this topic, much to my surprise. Do you perchance have a relevant link?
In my impression, your “existence” theory would imply that making an object from a subject should not have any influence on the usage of “to do.” Still the following sentences all seem similar concerning the existence of the persons in question:
- Who came to see you? (“who” = subject, no “to do”)
- Who(m) did you see? (“who(m)” = direct object, “to do”)
- Whose car hit you? (“whose car”= subject, no “to do”)
- Whose car did you notice? (“whose car” = direct object, “to do”)
I think there is no choice but to use “to do” in the second and fourth sentences, where the question word is (in) the direct object. So maybe there is some truth in my “subject” theory?
Thank you for your reply. Please let me clarify two things: First, I am not a grammarian, so my post was an attempt to explain something in layman’s terms. Second, I mentioned the “existence" angle only because the sentence in this exercise uses the verb "to exist." I did not intend to propose an “existence theory.”
On the contrary, my post simply suggests that English uses "do" forms in many questions, usually when we are asking about an activity and something or someone related to it. “Do” forms also are used for emphasis, as yewtwteiyty pointed out.
All of the sentences in both of your posts are quite correct. Finally, you may be on to something with your “subject” theory, but I’m not really in a position to judge that! :-)