Explanation:

Only statement 1st is correct.

• Mitochondria are membrane-bound organelles found in the cytoplasm of most eukaryotic cells. Unlike most other organelles, mitochondria have their own DNA, known as mtDNA. 

• Often referred to as the "powerhouses" of the cell, mitochondria are essential for producing energy needed for various cellular processes.  

• Mitochondria are inherited exclusively from the mother through the egg cell. 

• Mitochondrial DNA (mtDNA): mtDNA is prone to deletion mutations, where parts of the DNA are lost. These mutations can have significant consequences on cellular function.

• A deletion mutation in mtDNA makes the molecule smaller and less functional. Mutated mtDNA can outcompete healthy mtDNA during replication, causing a gradual decline in mitochondrial function. 

Hence option 1st is correct.