Implantation of an embryo normally occurs in what layer of the uterus?

A. Connective tissue that connects bone to bone: This describes a ligament, which links bones at a joint, not a tendon.
B. Connective tissue that covers muscles: Muscle coverings are layers like the epimysium or fascia; tendons are not the general covering of muscle.
C. Connective tissue that covers nerves: Nerves are wrapped by sheaths such as the epineurium and perineurium; tendons serve a different function.
D. Connective tissue that connects muscle to bone: Tendons are dense, collagen-rich structures that transmit the force of muscle contraction to bone.

A. Calcium (Ca⁺): This mineral plays roles in bone strength, muscle contraction, and clotting but is not involved in oxygen binding in hemoglobin.
B. Sodium (Na⁺): Sodium helps regulate fluid balance and nerve signaling, but it does not participate in oxygen transport.
C. Iron (Fe⁺): Iron within the heme groups of hemoglobin binds reversibly with oxygen, allowing red blood cells to transport it throughout the body.
D. Potassium (K⁺): Potassium maintains cell membrane potential and nerve conduction, not oxygen binding.