mesophyll 
The tissues of a leaf that are located in between the layers of epidermis and carry on photosynthesis, consisting of the palisade layer and the spongy parenchyma. Most mesophyll cells contain chloroplasts.

Mesophyll is the internal ground tissue located between the two epidermal cell layers of the leaf; and is composed of two kinds of tissues: the palisade parenchyma, an upper layer of elongated chlorenchyma cells containing large amounts of chloroplasts; and the spongy parenchyma, a lower layer of spherical or ovoid ...

Mesophyll:

Mesophyll is a type of tissue found in the leaves of plants. It is responsible for carrying out photosynthesis, which is the process by which plants convert sunlight into energy.

Consists of:

Mesophyll consists of two types of parenchyma cells, which are specialized cells that make up most of the plant's tissues. These cells are the spongy parenchyma cell and the palisade parenchyma cell.

Spongy parenchyma cell:

The spongy parenchyma cell is located in the lower part of the mesophyll. It is loosely packed and contains many air spaces, which allow for the exchange of gases such as carbon dioxide and oxygen. This cell also stores water and nutrients for the plant.

Palisade parenchyma cell:

The palisade parenchyma cell is located in the upper part of the mesophyll. It is tightly packed and contains many chloroplasts, which are responsible for carrying out photosynthesis. This cell also stores starch, which is a form of energy that plants use to carry out their life processes.

Both (A) and (B):

Mesophyll consists of both spongy parenchyma cells and palisade parenchyma cells. These cells work together to carry out photosynthesis and to provide the plant with the energy it needs to grow and survive.

None of these:

Option 'D' is incorrect as the correct answer is option 'C' which states that mesophyll consists of both spongy parenchyma cells and palisade parenchyma cells.