Q: Why do birds need a light-weight body?


Read this paragraph and choose the correct option from the provided answers:

Birds need a light-weight body in order to stay aloft. Even so, flying is hard work, and flight muscles need a constant supply of oxygen- and nutrient-rich blood. The organ systems of birds are adapted to meet these needs.

 Choices:

- for cooling

- water flotation

- food shortages

- to stay aloft


A:
to stay aloft