Question

multiple choice question
which is a characteristic of red blood cells?

they have no nucleus.
they help fight infections.
they are small fragments of cells.
they can move through intact blood vessel walls to enter tissue fluid.

Explanation:

Red blood cells are anucleate, meaning they lack a nucleus. They are responsible for transporting oxygen and carbon - dioxide, not for fighting infections (that's white blood cells' role), and they are not small fragments of cells (platelets are). Also, white blood cells can move through intact blood vessel walls to enter tissue fluid, not red blood cells.

Answer:

A. They have no nucleus.