Dendrochronology is

Which of the following supports a dense population of plankton and littoral vegetation?

The monomer $( X )$ involved in the synthesis of Nylon $6,6$ gives positive carbylamine test. If $10$ moles of $X$ are analyzed using Dumas method, the amount $($in grams$)$ of nitrogen gas evolved is $....$
Use: Atomic mass of $N ($in amu$) = 14$

Assertion : $Pb^{4+}$ compounds are stronger oxidizing agents than $Sn^{4+}$ compounds.
Reason : The higher oxidation states for the group $14$ elements are more stable for the heavier members of the group due to 'inert pair effect'.

Which of the following is a polyamide?

At $300 K$ , an ideal dilute solution of a macromolecule exerts osmotic pressure that is expressed in terms of the height $(h)$ of the solution $($density $=1.00 g cm ^{-3} )$ where h is equal to $2.00 cm$ . If the concentration of the dilute solution of the macromolecule is $2.00 g dm ^{-3}$, the molar mass of the macromolecule is calculated to be $X \times 10^4 g mol ^{-1}$. The value of $X$ is $...$ .
Use : Universal gas constant $(R)=8.3 J K ^{-1} mol^{-1}$ and acceleration due to gravity $( g )=10 m s ^{-2}$