Respuesta :
The correct answer is C, the rest of the options have an error with the date except for C.
C is the right answer.
The rest are wrong because..
A- no comma is needed after 2011
B- There should be a comma after 21 to separate the date and the year
D- no comma is needed after 2012
The rest are wrong because..
A- no comma is needed after 2011
B- There should be a comma after 21 to separate the date and the year
D- no comma is needed after 2012