Explanation:

- Children are often considered fragile. This means they can easily be affected by external factors.

- Parents therefore pay attention to the upbringing that covers psychological, emotional, and physical development.

- Option 1: Fragile, upbringing - Fits well as children are delicate (fragile), and upbringing is about nurturing them.

- Option 2: Robust, breeding - "Robust" is inappropriate as children are not typically strong in this context, and "breeding" refers more to animals.

- Option 3: Competitive, upgrading - These words don't relate well to children or parenting.

- Option 4: Aggressive, substitution - These terms don't logically fit the context of raising children.

- Option 5: Adamant, abeyance - These also don't relate to the context of child nurturing.