Which of the following metals becomes passive towards concentrated $HNO_3$?

What are $\underline{A}, \underline{B}, \underline{C}$ in the following reactions?
$(I)$ $(CH_3 CO_2)_2 Ca \xrightarrow{\Delta} \underline{A}$
$(II)$ $CH_3 CO_2 H \xrightarrow[Red\ P]{HI} \underline{B}$
$(III)$ $2 CH_3 CO_2 H \xrightarrow{P_4 O_{10}} \underline{C}$
$\underline{A} \quad \underline{B} \quad \underline{C}$

Glucose and mannose are

As we go from species to kingdom in a taxonomic hierarchy,the number of common characteristics

An inductance of $\frac{200}{\pi} \ mH$,a capacitance of $\frac{10^{-3}}{\pi} \ F$ and a resistance of $10 \ \Omega$ are connected in series with an $AC$ source of $220 \ V, 50 \ Hz$. The phase angle of the circuit is:

In which of the following compounds does the transition metal have a zero oxidation state?