Which of the following elements is doped into a fiber amplifier in an optical fiber communication system?

Which of the following statements is incorrect?

Which one of the following ions participates in the production of $ATP$ from the oxidation of glucose?

Zinc forms two important alloys,$(i)$ Brass and $(ii)$ German silver. Metals present in them mainly are

$Cu_2Cl_2$ with $HCl$ in the presence of oxidizing agents gives:

In the scheme given below,$X$ and $Y$,respectively,are:
$\text{Metal halide} \xrightarrow{\text{aq. NaOH}} \text{White precipitate } (P) + \text{Filtrate } (Q)$
$P \xrightarrow[\text{heat}]{\text{aq. } H_2SO_4, PbO_2 (\text{excess})} X (\text{a coloured species in solution})$
$Q$ $\xrightarrow[\text{warm}]{\text{MnO(OH)}_2, \text{Conc. } H_2SO_4} Y (\text{gives blue-coloration with KI-starch paper})$