The correct answer is option 1: Red blood cells (RBCs) have no nucleus, no mitochondria, and no endoplasmic reticulum.

Option 2 is incorrect because it states that RBCs have a nucleus, mitochondria, and endoplasmic reticulum. In reality, RBCs are unique among cells in that they do not have a nucleus. This lack of a nucleus allows RBCs to have more space to carry oxygen molecules.

Option 3 is incorrect because it states that RBCs have a nucleus and mitochondria, but no endoplasmic reticulum. While RBCs do lack a nucleus, they also lack mitochondria and endoplasmic reticulum.

Option 4 is incorrect because it states that RBCs have no mitochondria but do have endoplasmic reticulum. However, RBCs do not possess either mitochondria or endoplasmic reticulum.

In summary, option 1 correctly states that RBCs have no nucleus, no mitochondria, and no endoplasmic reticulum, which is a unique characteristic that allows RBCs to perform their specific function of delivering oxygen throughout the body.