people don't know the value of___they have until it's gone.A what B that C which D whose

people don't know the value of___they have until it's gone.A what B that C which D whose
people don't know the value of___they have until it's gone.A what B that C which D whose

people don't know the value of___they have until it's gone.A what B that C which D whose
A what作of的宾语和从句中have的宾语

b.what

应该选C

A.what