The graph is drawn between the applied force $F$ and the strain $(x)$ for a thin uniform wire. The wire behaves as a liquid in the part:

In the given stress-strain graph,what does point $D$ indicate?

The stress-strain graphs for materials $A$ and $B$ are shown in the figure. The graphs are drawn to the same scale.
$(a)$ Which of the materials has the greater Young's modulus?
$(b)$ Which of the two is the stronger material?

Assertion $(A)$: Ductile metals are used to prepare thin wires.
Reason $(R)$: In the stress-strain curve of ductile metals,the length between the points representing elastic limit and breaking point is very small.

The stress-strain graph of two wires $A$ and $B$ is shown in the figure. If $Y_{A}$ and $Y_B$ are Young's moduli of materials of wires $A$ and $B$ respectively, then

The diagram shows the stress versus strain curve for materials $A$ and $B$. From the curves,we infer that: