Mark the statement as true or false
(a) In unicellular organisms all the functions are performed by single cell.
(b) In the complex body of multicellular animals different functions are carreid out by different group of cells.
(c) In multicellular animals, a group of similar cells alongwith intercellular substances perform a specific function. such an organisation is called tissue.
(d) The functions of cells vary according to their structure.

Answer

### Step-by-Step Solution:

1. **Statement A**: "In unicellular organisms, all the functions are performed by a single cell."
- **Analysis**: Unicellular organisms, such as amoeba, consist of only one cell that carries out all necessary life functions, including digestion, reproduction, and respiration.
- **Conclusion**: This statement is **True**.

2. **Statement B**: "In the complex body of multicellular animals, different functions are carried out by different groups of cells."
- **Analysis**: In multicellular organisms, cells group together to form tissues, and each type of tissue performs a specific function. For example, muscle tissue is responsible for movement, while nervous tissue is involved in signaling.
- **Conclusion**: This statement is **True**.

3. **Statement C**: "In multicellular animals, a group of similar cells along with intercellular substances perform a specific function. Such an organization is called tissue."
- **Analysis**: Tissues are indeed formed by groups of similar cells that work together to perform a specific function, along with the intercellular substances that provide support and structure.
- **Conclusion**: This statement is **True**.

4. **Statement D**: "The functions of cells vary according to their structure."
- **Analysis**: While it is true that different types of cells have different structures, the statement implies that the function is solely dependent on structure. However, the function of a cell is primarily determined by its nucleus and the genetic information it contains, rather than just its structure.
- **Conclusion**: This statement is **False**.

### Final Answers:
- (a) True
- (b) True
- (c) True
- (d) False