Your taskFill in the gap in each sentence with the correct word or phrase.did we realizedid the last guests leavedid I understanddid he graspdid I appreciatedid the manager realizedid we seedid the referees restartdid she agreedid the board noticedid the company understanddid I discoverdid the reader find outwill you knowdid the committee make0 / 15 answeredYour score0 / 150%Keep practising! Focus on the explanations below.1Not until the lights came back on how frightened everyone had been. (we / realize)Correct answer: did we realize▸ Why?After a fronted "Not until", the main clause inverts with do-support: "did we realize". A common error is to keep statement order ("we realized") and forget the inversion.2Not until midnight the building. (the last guests / leave)Correct answer: did the last guests leave▸ Why?The inversion falls in the main clause: "did the last guests leave". Writing "the last guests left" ignores the obligatory inversion triggered by the fronted "Not until".3Only when the train finally stopped that we were at the wrong station. (I / understand)Correct answer: did I understand▸ Why?"Only when" fronted forces inversion in the main clause: "did I understand". The base verb follows "did", so "did I understood" is wrong.4Only after she had left the room what she had really meant. (he / grasp)Correct answer: did he grasp▸ Why?The fronted "Only after" clause triggers main-clause inversion: "did he grasp". Note the inversion uses "did" + base verb even though the time clause itself is past perfect.5Not until I read the report myself the true scale of the problem. (I / appreciate)Correct answer: did I appreciate▸ Why?Inversion goes in the main clause: "did I appreciate". The time clause keeps normal order ("I read the report"); only the main clause inverts.6Only then that he had been deceived all along. (the manager / realize)Correct answer: did the manager realize▸ Why?"Only then" is a restrictive adverbial that triggers inversion: "did the manager realize". Statement order ("the manager realized") would be ungrammatical after the fronted "Only then".7Not until the results were published how hard the students had worked. (we / see)Correct answer: did we see▸ Why?The main clause inverts: "did we see". The verb after "did" stays in its base form, so "did we saw" is wrong.8Only when the rain finally stopped the match. (the referees / restart)Correct answer: did the referees restart▸ Why?"Only when" fronted triggers inversion in the main clause: "did the referees restart". The plural subject still takes "did", and the verb stays in base form.9Not until he had apologized properly to speak to him again. (she / agree)Correct answer: did she agree▸ Why?Inversion in the main clause gives "did she agree". The time clause is past perfect, but the inverted main clause uses "did" + base verb.10Only after the audit was complete the missing funds. (the board / notice)Correct answer: did the board notice▸ Why?The fronted "Only after" clause forces main-clause inversion: "did the board notice". A frequent slip is "the board noticed", which keeps statement order.11Not until much later the true cost of the decision. (the company / understand)Correct answer: did the company understand▸ Why?The main clause inverts: "did the company understand". "Not until much later" sets the inversion in motion; the base verb follows "did".12Only when I got home that I had lost my wallet. (I / discover)Correct answer: did I discover▸ Why?Inversion in the main clause gives "did I discover". The verb stays in base form after "did", so "did I discovered" is wrong.13Not until the very last page who the murderer really was. (the reader / find out)Correct answer: did the reader find out▸ Why?The main clause inverts: "did the reader find out". The multi-word verb "find out" keeps its base form after "did".14Not until you have tried it yourself how difficult it really is. (you / know)Correct answer: will you know▸ Why?The lead-in "have tried" points to the future, so the inverted modal is "will you know" — not "did you know". The inversion still lands in the main clause.15Not until every option had been considered a final decision. (the committee / make)Correct answer: did the committee make▸ Why?The fronted "Not until" clause forces main-clause inversion: "did the committee make". The base verb follows "did", so "made" or uninverted "the committee made" would both be wrong.Check AnswersPlease answer at least one question first.Found an error in this exercise? Let us know.