Incorrect:

The agreeing is not legal unless everyone signs his name.

Correct:

The agreement is not legal unless everyone signs his name.

Exercises:

Part A: Choose the correct answer.

Unless protected areas are established, the Bengal tiger, the blue whale, and the California condor face _________ of extinction.

(A) possible  (B) the possibility  (C) to be possible  (D) possibly 

Part B: Choose the incorrect word or phrase and correct it.

Because  blood from different individuals may different  in the type of antigen on the surface of the red cells and the type of antibody in the plasma, a dangerous reaction can occur  between the donor and  recipient in a blood transfusion.

Subject-Verb Inversion

Inversion of Subject and Verb

The subject comes before the verb in all but a few special situations. In these situations the word order of the core parts is inverted and the verb is placed before the subject.

There are 18 cases when inverted order is needed:

1. negative introductory phrase 2. introductory adverbial (in, down, prepositional phrase) 3. introductory –ed 4. comparative 5. introductory comparative 6. as 7. so… that... 8. had, should, were 9. there is 10 introductory –ing 11. here is 12. emphasis 13. questions 14. "story speech" 15. “so do I”/ “neither do I” 16. nor 17. introductory adjective 18. introductory few, such, so, little

1. a sentence begins with a "negative" word or expression such as: When a sentence begins with only and a time expression, the subject and verb of the main clause are inverted. only + time: only once, only at night, only after, etc.

hardly hardly ever neither never no sooner . . . than nor not often not once not only ... as well not only . . . but also not until not until nowhere

not only on no account barely only only by only in this way only then rarely scarcely scarcely ... when seldom so under no circumstances at no time

Examples:

Never do I sleep. Only at night can I study. In no way could I help you with your Japanese grammar question. I believe that only rarely will I need your help. Not until I got home did I realize that my shoes were untied.

2. When an adverb such as down, in, out, up is placed at the beginning of the sentence.

Examples:

Into the room ran the lady. First comes love, then comes marriage. After A comes B, then comes C, next comes D. Down came the rain and washed the spider out.

3. A sentence begins with a Past Participle phrase

Examples:

Found in San Francisco is Lombard Street, the so-called “crookedest street in the world.” Lost among the old tables and chairs was the priceless Victorian desk. Located between San Francisco and Marin County is the Golden Gate Bridge.

4. After comparing subjects of the verb, not objects.

Examples:

Cheetahs run faster than do antelopes. You speak Chinese better than do I. Jessica is more interested in Computer Science than is Benjamin.