A bit confused with Not until ... do

I found a sentence in test.

Not until several years after a war has ended _________ to feel the severe psychological damage it can cause.

(A) do many of its veterans begin
(B) many of its veterans begin
(C) and many of its veterans begin
(D) many of its veterans beginning

I chose B answer, but the correct answer (due to test) was A.

Could anybody explain why here we should use do clause?

Solution 1:

When a sentence starts with 'Not until', as well as many other phrases, the grammar needed is Inversion, which means using the interrogative form of whatever tense the verb is in. 'begin' is in Simple Present, so 'do' is required. Here are some examples:

Not until John apologizes, will I go out with him again.

Not until the teacher explained it again, did I understand.

Not until I've been working for ten years, will I have saved up enough money to pay off my student loan.

Not until the temperature falls to O degrees C does water turn to ice.

There is a similar question at :Not until ( sentence ) + do (sentence)

but I believe I've explained it slightly differently.

"Not till I got home did I realise my wallet was missing."

(Cambridge Dictionaries Online)

http://dictionary.cambridge.org/grammar/british-grammar/inversion