Red blood cells — task. Biology CBSE Live product, Class 9 (2025-26).

Choose the best answer:

1. Human blood normally has a pH range of ________.

neutral
7.35–7.45
7.5–7.7
6.8–7.0

2. Which structural feature of mammalian RBCs helps increase surface area for gas exchange?

Biconcave shape
Spindle-shaped
Spherical
Cuboidal

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