A sparrow is a primary consumer when it eat seeds, but becomes secondary consumer when it eats __________.

Insects

The correct answer is Option (4) → Insects

A sparrow is a primary consumer when it eats seeds, as it is directly consuming plant material. However, when it eats insects, it becomes a secondary consumer because it is now consuming an animal (the insect), which is a primary consumer itself in many ecosystems.

So, the correct answer is insects