When total revenue is at a maximum?

My answer is also option (D)

Answer will be option ____________d

1. When total revenue is at a maximum The correct answer was: d. none of the above is correct.. none of the above is correct. 

I CHOOSE D ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

D

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Thanks

The answer is : Option ( D )

D.............................................................

D.............................................