If the density of the material increases,the value of Young's modulus

Copper of fixed volume $V$ is drawn into a wire of length $l$. When this wire is subjected to a constant force $F$,the extension produced in the wire is $\Delta l$. Which of the following graphs is a straight line?

Two rods of same material and volume having circular cross-section are subjected to tension $T$. Within the elastic limit,the same force is applied to both the rods. If the diameter of the first rod is half of the second rod,then the ratio of the extension of the first rod to the second rod will be: (in $: 1$)

Four wires of the same material are stretched by the same load. Which one of them will elongate the most if their dimensions are as follows?

One end of a horizontal thick copper wire of length $2L$ and radius $2R$ is welded to an end of another horizontal thin copper wire of length $L$ and radius $R$. When the arrangement is stretched by applying forces at two ends,the ratio of the elongation in the thin wire to that in the thick wire is:

$5 \,m$ long aluminium wire $(Y = 7 \times 10^{10} \,N/m^2)$ of diameter $3 \,mm$ supports a $40 \,kg$ mass. In order to have the same elongation in a copper wire $(Y = 12 \times 10^{10} \,N/m^2)$ of the same length under the same weight, the diameter should be (in $mm$):