Final answer:
The grid in a structure is not rigid or permeable, but it is visible, providing support without being easily noticeable.
Step-by-step explanation:
The correct answer is b) Visible. A grid in a structure is usually made up of thin, interconnected elements (such as beams or bars) that provide support without being easily noticeable. These elements can be made of various materials depending on the type of structure, such as steel, concrete, or wood.
For example, in a building, the grid of steel beams and columns provides structural support while also allowing for open spaces and visible facades. Similarly, in a fence, a grid of wire or metal bars holds the structure together while still allowing visibility through the gaps.
Therefore, while the grid is supportive, it is not rigid as it can be flexible to some degree. It is also not permeable as it does not allow substances to pass through easily. However, it is often designed to be visible as part of the aesthetic appeal or function of the structure.