The tissue where cells are thin-walled, living, isodiametric along with intercellular spaces is

The correct option is Parenchyma.

Let us break down the features of the tissue mentioned in the question step-by-step to understand why Parenchyma is the correct answer:
1. Thin-walled cells: Parenchyma cells have thin cell walls made primarily of cellulose.
2. Living cells: They are living cells with active protoplasts at maturity, functioning in storage, photosynthesis, and secretion.
3. Isodiametric shape: Parenchyma cells are typically isodiametric, meaning they are roughly spherical or equal in all dimensions, allowing them to pack together while leaving gaps.
4. Intercellular spaces: Due to their rounded or oval shape and loose packing, there are distinct intercellular spaces present between the cells.

Let us briefly look at the other options to see why they do not fit the description:
- Arenchyma: This is a specialized type of parenchyma (often found in aquatic plants) that contains large, exaggerated air cavities rather than standard small intercellular spaces.
- Collenchyma: These cells have irregularly thickened cell walls (thickened at the corners with pectin and cellulose) and typically lack intercellular spaces.
- Prosenchyma: These are elongated, fiber-like plant cells with pointed ends, which are primarily structural and do not exhibit the typical isodiametric, thin-walled structure with prominent intercellular spaces.

Therefore, the tissue that perfectly matches all the given characteristics is parenchyma.