From the following identify the groups that exhibit negative resonance $(-R)$ effect when attached to conjugated system

$$ \begin{array}{ccccc} \text { Formyl } & \text { Amino } & \text { Alkoxy } & \text { Cyano } & \text { Nitro } \\ A & B & C & D & E \end{array} $$

The diffraction pattern of crystalline solid gave a peak at $20=60^{\circ}$. What is the distance ( in cm ) between the layers which gave this peak?

( $\lambda$ of $X$-rays is $1.54 \mathring{A}$ ) $\left(\sin 30^{\circ}=0.5, \sin 60^{\circ}=0.866 ; n=1\right)$

The concentration of 1 L of $\mathrm{CaCO}_3$ solution is 1000 ppm . What is its concentration in mol $\mathrm{L}^{-1}$ ?

$$ (\mathrm{Ca}=40 \mathrm{u}, \mathrm{O}=16 \mathrm{u}, \mathrm{C}=12 \mathrm{u}) $$