The correct answer is option 4, that is, GCGATT.  
Complementary strand refers to either of the two chains, which forms a double helix of DNA, with corresponding positions on the two chains comprising of a pair of complementary bases. It is a section of one nucleic acid, which is bonded to another by an alignment of base pairs.  
In nature, complementarity refers to the base principle of DNA transcription and replication as it is a characteristic shared between the two RNA or DNA sequences, such that when they are arranged antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary.  
 
        
                    
             
        
        
        
Answer:
To turn sugars into energy
Explanation:

- Mitochondria are main sites of aerobic respiration. They are miniature biochemical factories where food stuffs are completely oxidised to carbon dioxide and water. 
- The energy (ATP) produced in the mitochondria helps to perform various energy requiring processes. 
- Because of the formation of ATP in mitochondria it is called power house of the cell.

- Photosynthesis: Light reaction (in thylakoids), Dark reaction (in stroma).
- Storage of starch.