Tax Question re: 2 year exemption - CA

[Lauren Ascher]

Hi all,
I'm planning to sell a condo in Los Angeles.  I sold my duplex for a profit on 10-1-15, and bought my condo on 9-4-15.  When I sell my condo, what date of sale would qualify me for the two year exemption to not pay taxes on gains?

A) 10-1-17 (two years from the sale of the duplex which I used for an exemption)
B) 9-4-17 (two years from the close on the condo)
C) 1-1-2018 (because the exemption was used on 2015 return, it cannot be used on 2016 or 2017).

Please advise!
Thanks