When the old oil painting are kept in the atmosphere for a longer time the tracer of gas present in atmosphere converts lead oxide (PbO) into PbS which is black in colour.
PbO
Litharge
H2S
────▶
PbS
Lead
solphide
(Black)
H2O2
────▶
PbSO4
Lead
sulphate
(White)
Therefore, these paintings get transhed. It can be restored by keeping then in H2O2 solution for sometime as a result of which lead sulphide is oxidised to lead sulphate. So, A is true but R is false.