Why "serait" not "seraient"

Question

"J'en ai vu une autre hier qui avait un grenier et un sous-sol, ce qui serait parfait..." I thought of this as BOTH attic and basement being useful for storage and used third person plural, "seraient."  Why wasn't this correct?

Chris Wirt · Accepted Answer

The clue is ce qui (literally: that which), the subject of the clause, which is singular. It refers back to a general idea and is always singular.
J'en ai vu une autre hier qui avait un grenier et un sous-sol, ce qui serait parfait -- I saw another one yesterday that had an attic and a basement, which would be perfect.

Jim Jones · Answer

Hi Adrienne,I see "une autre" as being the subject of the following clause and therefore "serait""The other was perfect"    because of the enhanced storage facilities.Bonne journéeJim