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Companion cells are the cells which remain associated with the sieve tube elements of the phloem. Since sieve tubes have perforated cell walls and companion cells remain associated with them companion cells help in maintaining the pressure gradient of the sieve tube element and thus help in the transportation of food.

Companion cells are components of the phloem tissue. They remain associated with the sieve tube elements of the phloem tissue. Phloem is a vascular tissue and is present for conduction in vascular plants 

Functions of companion cell are as follows: 

● Companion cells help in maintaining the pressure gradient of the sieve tube elements and thus help in conduction of food through sieve tubes.

● It plays role in conduction of food.

There are certain plants which are living in extreme conditions and it is possible due to the presence of certain distinctive features:

● Plants living in extreme dry habitats have a thick epidermal layer which prevents the loss of water.

● In desert plants, they have a thick waxy cuticle over the outer surface which prevents the loss of water.

There are certain levels which form the basis of classification of tissues present in plants and animals:

● On the basis of movement - Plants are stationary and they do not move while animals move from one place to another for various reasons. Therefore, the tissues required by plants are those which provide mechanical strength and mostly they are dead in nature whereas in animals the tissues are living as they need to move.

● On the basis of the pattern of growth - The growth pattern of plants and animals also differs. Plants have certain regions which continue to divide throughout the life while the same thing does not happen in case of some other regions. There is more uniform cell growth in animals as compared to plants. So, tissues are classified considering the pattern of growth.

● On the basis of the structural organization - The structural organization of animals is far more complex as compared to plants. Therefore, there are differences in tissues which are responsible for the structural organization and form a basis of classification.

Nuclei is located at the periphery in striated muscles. All other muscles are uninucleate and do not have nucleus at the periphery. 

Therefore, the correct option is (c) striated muscles

Apical and intercalary meristems are not themselves permanent tissue instead they differentiate to form different types of permanent tissues.

Functions of bone: 

● The complete framework of the body is formed of bone which provides support to the complete body. 

● It provides anchorage to the muscles and support to the organs. 

● Bones also help in the movement. Functions of cartilage: 

● It smoothens the bone surfaces at joints like in tip of nose, ears. 

● It is not very much rigid as bones and not very much elastic like muscles. It is flexible to some extent and is present where littlie flexibility is required. 

For example – Cartilages are present in between vertebral column.

The simple epithelium is composed of a single layer of cells. This type of epithelial tissue forms the lining of blood vessels and alveoli. Thin layer of cells facilitates exchange of substances; in such cases.

Cells are column-shaped in columnar epithelium. Columnar epithelium facilitates secretion and absorption. For example; the lining of intestine is composed of columnar epithelium. In some organs, columnar epithelium has cilia present on the outer surface. Cilia facilitate movements of certain substances. The ciliated epithelium in the respiratory tract pushes the mucus forward.