Which of the following resistivity ( $\rho$ ) $v/s$ temperature $( T )$ curves is most suitable to be used in wire-bound standard resistors?

Two metal wires of identical dimensions are connected in series. If $\sigma_1$ and $\sigma_2$ are the conductivities of the metal wires respectively,the effective conductivity of the combination is

$A$ wire of a certain material is stretched slowly by $10\%$. Its new resistance and specific resistance become respectively:

Resistance of a wire at $0^{\circ} C, 100^{\circ} C$ and $t^{\circ} C$ is found to be $10 \Omega, 10.2 \Omega$ and $10.95 \Omega$ respectively. The temperature $t$ in Kelvin scale is $\qquad$

$A$ metal wire of length $L$ and radius $r$ has a resistance $R$. If a wire of the same metal of length $2L$ and radius $3r$ is taken,then what will be its resistance?

What is electrical resistance $(R)$? On which factors does the resistance value depend?