English/Writing-Structure-19-ID

Which example correctly punctuates this sentence?

After we got home she realized she had left her purse.

o  After we got home she realized she had left her purse.
o  After we got home, she realized she had left her purse.
o  After, we got home she realized she had left her purse.
o  After we got home she realized she had, left her purse.