Copper turnings when heated with concentrated sulphuric acid will give:

How many $S-OH$ bonds are present in Caro's acid?

$A$ sulphate of a metal $(A)$ on heating evolves two gases $(B)$ and $(C)$ and an oxide $(D).$ Gas $(B)$ turns $K_2Cr_2O_7$ paper green while gas $(C)$ forms a trimer in which there is no $S-S$ bond. Compound $(D)$ with $HCl$ reacts to form a compound $(E)$ which exists as a dimer. Compounds $(A)$,$(B)$,$(C)$,$(D)$ and $(E)$ are respectively:

Which one of the following is most acidic?

Identify the correct order of acidity of hydrides of $16^{th}$ group elements from the following.

Which of the following options is $incorrect$?