The stress-strain curve for glass during a tensile test would exhibit a sudden break (option D). This means that the curve would show a sudden drop in stress or load at a certain point, indicating a brittle failure.

Here is a detailed explanation of why the stress-strain curve for glass exhibits a sudden break:

1. Introduction to Tensile Testing:
Tensile testing is a common method used to determine the mechanical properties of materials, including their strength, elasticity, and ductility. During a tensile test, a sample material is subjected to a gradually increasing tensile load until it reaches its breaking point.

2. Stress-Strain Curve:
The stress-strain curve is a graphical representation of the relationship between stress (force per unit area) and strain (deformation) experienced by a material under tension. The curve provides valuable information about the material's behavior and mechanical properties.

3. Elastic Region:
When a material is subjected to a tensile load, it initially deforms elastically, meaning it can return to its original shape after the load is removed. In this region, the stress-strain curve is linear and follows Hooke's law. The material's response is described by its Young's modulus, which represents its stiffness.

4. Yield Point:
At a certain stress level, known as the yield point, the material undergoes permanent deformation or plasticity. However, glass does not exhibit a well-defined yield point because it is an amorphous material and lacks crystal structure.

5. Brittle Behavior of Glass:
Unlike metals and some other materials, glass does not exhibit significant plastic deformation before failure. It is a brittle material, which means it undergoes very limited plastic deformation and fractures abruptly without warning.

6. Sudden Break in the Curve:
Therefore, when a tensile load is applied to glass, the stress-strain curve shows a sudden break or drop in stress at the point of failure. This sudden break indicates that the glass has reached its ultimate tensile strength and has fractured. The fracture surface of glass is typically smooth and shiny, indicating a brittle failure.

In conclusion, the stress-strain curve for glass during a tensile test exhibits a sudden break because glass is a brittle material that undergoes limited plastic deformation before failure. Understanding the stress-strain behavior of glass is crucial for designing and engineering glass structures to ensure their safety and reliability.