Please predict whether a double displacement reaction will occur PLEASE HELP ME?

Question

K2S+CuSO4
NH4OH+H2C2O4
KOH+NH4Cl
NaC2H3O2+HCL
Na2CrO4+Pb(C2H3O2)2
(NH4)2SO4+NaCl
BiCl3+NaOH
KC2H3O2+CoSO4
Na2Co3+HNO3
ZnBr2+K3PO4

I still don't understand

Answer 1

Double displacement means whether or not a reaction will occur resulting in an insoluble precipitate.

CuS ppt, so yes
No
No
Could be yes. HC2H3O2 is a slightly ionized acid, so your teacher could be looking for a yes.
PbCrO4 ppt, yes
No
Bi(OH)3 ppt yes
Na2CO3 + 2HNO3 ===> 2NaNO3 + CO2 + H2O so yes
Zn3(PO4)2, yes