Select the correct pair.

To identify the correct pair, let's analyze each option step-by-step based on plant anatomy:

1. Large colorless empty cells in the epidermis of grass leaves:
These cells are known as bulliform cells (or motor cells), not subsidiary cells. Subsidiary cells are specialized epidermal cells bordering guard cells. Thus, this pair is incorrect.

2. In dicot leaves, vascular bundles are surrounded by large thick-walled cells:
These surrounding cells form the bundle sheath. Conjunctive tissue is the parenchymatous tissue present between xylem and phloem in roots. Thus, this pair is incorrect.

3. Cells of medullary rays that form part of cambial ring:
During secondary growth in dicot stems, the cells of medullary rays adjoining the intrafascicular cambium become meristematic and form the interfascicular cambium. Together, the intrafascicular and interfascicular cambiums form a continuous cambial ring. Therefore, this pair is correct.

4. Loose parenchyma cells rupturing the epidermis and forming a lens-shaped opening in bark:
These cells are called complementary cells, and the lens-shaped opening is a lenticel. Spongy parenchyma is found in the mesophyll of leaves. Thus, this pair is incorrect.

Therefore, the only correctly matched pair is:
Cells of medullary rays that form part of cambial ring - Interfascicular cambium