Which of the following is not a synthetic polymer?

When a body of mass $1.0\, kg$ is suspended from a certain light spring hanging vertically,its length increases by $5\, cm$. By suspending a $2.0\, kg$ block to the spring,if the block is pulled through $10\, cm$ and released,the maximum velocity in $m/s$ is: (Acceleration due to gravity $g = 10\, m/s^2$)

Negation of the statement "The payment will be made if and only if the work is finished in time." is

Consider a gas phase reaction which occurs in a closed vessel: $2A \rightarrow 4B + C$. The concentration of $B$ is found to be increased by $5 \times 10^{-3} \ mol \ L^{-1}$ in $10 \ s$. The rate of disappearance of $A$ (in $mol \ L^{-1} \ s^{-1}$) is:

Some physical quantities are given in List-$I$ and their related units are given in List-$II$. Match the correct pairs.

List-$I$	List-$II$
$(A)$ Magnetic field intensity	$(i)$ $Wb$
$(B)$ Magnetic flux	(ii) $Wb \cdot m^{-2}$
$(C)$ Magnetic pole strength	(iii) $A \cdot m$
$(D)$ Magnetic induction	(iv) $A \cdot m^{-1}$

The equation of the radical axis of the pair of circles $7x^2+7y^2-7x+14y+18=0$ and $4x^2+4y^2-7x+8y+20=0$ is