Explanation:

- Option 1: Sex ratio

- Definition: The sex ratio refers to the number of males for every 100 females in a population.

- Relevance: It does not relate to the maximum number of births but to gender distribution.

- Option 2: Fecundity

- Definition: Fecundity is the biological maximum potential for reproduction, often referring to the potential reproductive capacity of an individual or population.

- Relevance: Correct answer. This term embodies the biological potential for births.

- Option 3: Fertility

- Definition: Fertility refers to the actual production of offspring. It counts the real number of children born per woman.

- Relevance: While related, it doesn't define the biological maximum.

- Option 4: Natural increase

- Definition: Natural increase measures population growth based on the difference between birth and death rates.

- Relevance: It doesn’t denote the number of births directly but net growth.