Final answer:
The comma rule in the example sentence is used after an introductory phrase, which sets the stage for the main action 'William ducked'. No specific rule named 'comma rule2' exists, and options 1, 3, and 4 don't apply since the sentence doesn't contain coordinating adjectives, conjunctions, or an appositive. None of the above option is follow.
Step-by-step explanation:
The comma rule used in the sentence 'William ducked behind the wide wooden desk, hoping that Sarah wouldn't see him.' is an example of a comma used after an introductory phrase. This rule applies when the sentence begins with words that set the stage for the main action, which, in this case, is 'William ducked.' The phrase 'hoping that Sarah wouldn't see him' introduces the action and provides context to William's behavior.
Furthermore, no comma rule is specifically called "comma rule2" or similar in standard English grammar terminology. Therefore, options 1, 3, and 4 can be disregarded. Option 2, appositive, is also incorrect because the sentence does not contain an appositive phrase. Instead, it uses a participle phrase as an introductory element. Moreover, when looking at standard comma rules, introductory phrases typically should be followed by a comma to separate them from the main clause, which is the case in this sentence.