For which material does resistivity decrease with an increase in temperature?

Two conductors are made of the same material and have the same length. Conductor $A$ is a solid wire of diameter $1 \ mm$. Conductor $B$ is a hollow tube of outer diameter $2 \ mm$ and inner diameter $1 \ mm$. Find the ratio of resistance $R_A$ to $R_B$.

Two wires of equal diameters,lengths $l_1, l_2$ and having resistivities $S_1, S_2$ respectively are joined in series. The equivalent resistivity of the combination is

With an increase in temperature,the resistivity of a conductor ........ and the resistivity of a semiconductor ....... .

The resistance of a resistance wire is $5\,\Omega$ at $50\,^{\circ}\text{C}$ and $6\,\Omega$ at $100\,^{\circ}\text{C}$. The resistance at $0\,^{\circ}\text{C}$ will be ............. $\Omega$.

The resistance of the bulb filament is $100 \ \Omega$ at a temperature of $100^{\circ} C$. If its temperature coefficient of resistance is $0.005 \ ^{\circ} C^{-1}$,at what temperature will its resistance become $200 \ \Omega$ (in $^{\circ} C$)?