Maybe this is unnecessary think,but I have thought it many times,too.Of course,I feel confusion about the J.M.'s comment.(Mr. J.M. is wonderful man who always break up my concept that have shape long time. :)).So I sure some built-in function is classified as option by WR.In an certain time,you can get this class of function by:

EntityClassList["WolframLanguageSymbol"] 

But I cannot reproduce it now(I'm in version 11.0.1),I don't sure the low version MMA can reproduce it or not.There is two screenshot I keep:

• First

http://o8aucf9ny.bkt.clouddn.com/2016-12-13-18-47-26.png

• Second http://o8aucf9ny.bkt.clouddn.com/2016-12-13-18-50-25.png

As we can see,there are $757$ function is classified as option names.After some thinking,I think this method can get all of option names:

Select[ToExpression[ DeleteCases[ CanonicalName[ Complement[EntityList["WolframLanguageSymbol"], EntityList[ EntityClass["WolframLanguageSymbol", "Autoevaluating"]]]], _?(StringStartsQ["$"])]], SyntaxInformation[#] == {} &] 

{Above,AccuracyGoal,ActiveStyle,AdjustmentBoxOptions,After,Algebraics,Alignment,AlignmentPoint,All,AllowedDimensions,AllowGroupClose,AllowInlineCells,AllowLooseGrammar,AllowReverseGroupClose,AlternateImage,AlternativeHypothesis,AltitudeMethod,AmbiguityFunction,AnchoredSearch,AnimationDirection,AnimationRate,AnimationRepetitions,AnimationRunning,AnimationRunTime,AnimationTimeIndex,Anonymous,Antialiasing,Appearance,AppearanceElements,...}

It's not $757$(Actually the number is $909$),but it's very colsely.

Maybe this is unnecessary think,but I have thought it many times,too.Of course,I feel confusion about the J.M.'s comment.(Mr. J.M. is wonderful man who always break up my concept that have shape long time. :)).So I sure some built-in function is classified as option by WR.In an certain time,you can get this class of function by:

EntityClassList["WolframLanguageSymbol"] 

But I cannot reproduce it now(I'm in version 11.0.1),I don't sure the low version MMA can reproduce it or not.There is two screenshot I keep:

• First

http://o8aucf9ny.bkt.clouddn.com/2016-12-13-18-47-26.png

• Second http://o8aucf9ny.bkt.clouddn.com/2016-12-13-18-50-25.png

As we can see,there are $757$ function is classified as option names.After some thinking,I think this method can get all of option names:

Select[ToExpression[ DeleteCases[ CanonicalName[ Complement[EntityList["WolframLanguageSymbol"], EntityList[ EntityClass["WolframLanguageSymbol", "Autoevaluating"]]]], _?(StringStartsQ["$"])]], SyntaxInformation[#] == {} &] 

{Above,AccuracyGoal,ActiveStyle,AdjustmentBoxOptions,After,Algebraics,Alignment,AlignmentPoint,All,AllowedDimensions,AllowGroupClose,AllowInlineCells,AllowLooseGrammar,AllowReverseGroupClose,AlternateImage,AlternativeHypothesis,AltitudeMethod,AmbiguityFunction,AnchoredSearch,AnimationDirection,AnimationRate,AnimationRepetitions,AnimationRunning,AnimationRunTime,AnimationTimeIndex,Anonymous,Antialiasing,Appearance,AppearanceElements,...}

It's not $757$(Actually the number is $909$),but it's very colsely.