What caused the tree to fall? What疑問代名詞 caused動詞 the tree名詞 to fall不定詞 ; 該句是疑問句為何沒有助動詞而將動詞搬到前面?

cause:-
Do not say "cause that someone does something";
Say "Cause someone to do something"
cause to make something happen, especially something bad:-
eg--:"-Bad weather" has caused the tree to fall.----(aux.verb=has;----v=caused----v--n--inf to---)
-----What has caused the tree to fall ?--------HAS CAUSED
-----"Bad weather"
eg:-"The worm "caused the tree to fall-------(v=caused----n-- inf. to----)
------What caused the TW tree to fall ?----------------CAUSED
-----"The Taiwan Worms called Choco."
auxiliary---adj
auxiliary---an auxiliary motor,piece of equipmemt etc is kept ready to be used if the main one stops working properly;am auxiliary power supply;
auxiliary verb-n--
a verb that is used with another verb to show its tense, person, mood etc. In English the auxiliary verbs are "be","do", "have" "caused"(as in I am eating,I do go, I didn't go, I have gone, the trees have caused; the tree caused, --the root cause caused the tree to fall ?!----Choco powdering is the main cause of root disease (that) caused the tree to fall ?!)

你可以用答句的結構來檢查問句的主詞是那一個字：
What is your name?
My name is Paul.
所以問句裡的疑問代名詞what是「主詞補語」，name才是「主詞」。
這時問句需要「倒裝」，把「動詞」或「助動詞」移到主詞的前面。動詞is需移到主詞之前。

What do you want?
I want something to eat.
what是問句的受詞，you是主詞，故增加一個助動詞do在主詞前，形成問句的倒裝結構。

Who gave you that book?
John did.
問句的主詞是疑問代名詞who是「主詞」，you是間接受詞，book是直接受詞。
這時的問句「不可倒裝」。

What caused the tree to fall?
這句裡的主詞是what，tree是受詞，to fall是受詞補語。
所以這問句「不可倒裝」。

結論：主詞是「疑問代名詞」時，疑問句的句構不會倒裝（移動助動詞或動詞到主詞之前）。

此外，將句尾音調上提的問句（用來確認所聽到的資訊是否正確）也不需倒裝。如：
B: How old are you?
A：I am eighty years old.
B: （You are） eighty years old? (句尾語調提高，可省略前面括號內的文字）
A: Yes, I AM. （am會加強語氣）

What caused the tree to fall?這種用疑問字開頭的句子，其語調在句尾是下降的。

英語的文法 只是一般原則的歸納與綜合.常用的日常用句例外一堆.請你不要本末倒置.

就拿你的問題 "英語疑問句"來說: 英語文法把疑問句分作2類 (1)yes-no questions (2)wh-questions

1. y-n questions

像是 Do you like me? Are you going? 這類是從 "肯定句型"根據 "助動詞/主詞 句中 位置的交換"所形成的疑問句

2. wh-questions
像是 who framed the Rabbits? When will you come?這類的.這種類的疑問句 當疑問的目標會是預期答案的主詞 的時候 就不會有 對調位置的需要

例子們:
Q: who cut the tree? (不須對調)
A: He did.

Q: what did he have? (對調)
A: He had some soup.

3. 你又要把這隻文法背起來了嗎? 請你不要再犯錯,本末倒置了好嗎?

What caused the tree to fall? ←← "what"係疑問代名詞，無助動詞，這句子符合文法。
What did cause the tree to fall? ←← "what"係疑問代名詞，"did"(助動詞)是強調語氣用，這句子符合文法。

疑問句不一定都要有助動詞