The cell wall of which of the following is made of peptidoglycan?

Bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ lost their original labels. They were labelled $A$ and $B$ for testing. $A$ and $B$ were separately taken in a test tube and boiled with $NaOH$ solution. The end solution in each tube was made acidic with dilute $HNO_3$ and then some $AgNO_3$ solution was added. Substance $B$ gave a yellow precipitate. Which one of the following statements is true for this experiment?

Consider a solid insulating sphere of radius $R$ with charge density varying as $\rho = \rho_0 r^2$ (where $\rho_0$ is a constant and $r$ is measured from the centre). Consider two points $A$ and $B$ at distances $x$ and $y$ respectively from the centre,such that $x < R$ and $y > R$. If the magnitudes of the electric fields at points $A$ and $B$ are equal,then:

In the following compounds,the order of acidity is:
$(I)$ Phenol
$(II)$ $p$-Cresol ($4$-methylphenol)
$(III)$ $m$-Nitrophenol
$(IV)$ $p$-Nitrophenol

Which of the following is a low spin complex?

If $D, E$ and $F$ are respectively the mid-points of $AB, AC$ and $BC$ in $\triangle ABC$,then $\overrightarrow{BE} + \overrightarrow{AF}$ is equal to :