Which bone is a large triangular bone at the base of the spine?

Which bone is a large triangular bone at the base of the spine?

• A. Sacrum
• B. Ilium
• C. Femur
• D. Tibia

Answer: (A)

The main idea is recognizing the sacrum as the large triangular bone at the base of the spine. It’s formed by five fused vertebrae and sits between the two hip bones, forming the back part of the pelvic girdle and carrying much of the body's weight into the pelvis. Its broad top, called the base, connects with the last lumbar vertebra, while its pointed bottom, the apex, points toward the coccyx. The sacrum also helps anchor the pelvis with the sacroiliac joints and contains openings (sacral foramina) for nerves. The other bones listed don’t fit this description. The ilium is the wing-like part of the hip bone on the sides, not at the base of the spine. The femur is the thigh bone, and the tibia is the shin bone in the leg.

The main idea is recognizing the sacrum as the large triangular bone at the base of the spine. It’s formed by five fused vertebrae and sits between the two hip bones, forming the back part of the pelvic girdle and carrying much of the body's weight into the pelvis. Its broad top, called the base, connects with the last lumbar vertebra, while its pointed bottom, the apex, points toward the coccyx. The sacrum also helps anchor the pelvis with the sacroiliac joints and contains openings (sacral foramina) for nerves.

The other bones listed don’t fit this description. The ilium is the wing-like part of the hip bone on the sides, not at the base of the spine. The femur is the thigh bone, and the tibia is the shin bone in the leg.