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?

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.

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