The correct answer is option 1: Mitochondria.

Red blood cells (RBCs), also known as erythrocytes, are specialized cells that transport oxygen throughout the body. One of the characteristic features of RBCs is that they lack a nucleus and other organelles, such as mitochondria. Mitochondria are the organelles responsible for carrying out aerobic respiration, a process that produces energy in the form of ATP.

In cells that contain mitochondria, aerobic respiration occurs in the mitochondria, where glucose is broken down in the presence of oxygen to produce ATP. However, since RBCs do not have mitochondria, they are unable to perform aerobic respiration. Instead, RBCs rely on a different metabolic pathway called anaerobic respiration, which occurs in the cytoplasm and yields a smaller amount of ATP.

In anaerobic respiration, glucose is broken down without the need for oxygen, producing a byproduct called lactate. This metabolic pathway allows RBCs to generate energy without the use of mitochondria.