The correct answer is option 4 - 33.

Vertebrae are the individual bones that make up the spine or backbone. In a human being, the spine consists of several vertebrae. The total number of vertebrae in a human varies depending on the region of the spine.

There are 7 cervical vertebrae, which are located in the neck region. The thoracic region contains 12 vertebrae, which are attached to the ribs. The lumbar region has 5 vertebrae, which are in the lower back. Additionally, there are 5 fused sacral vertebrae in the sacrum and 4 fused coccygeal vertebrae in the coccyx or tailbone.

Adding up these numbers, we get a total of 7 cervical vertebrae + 12 thoracic vertebrae + 5 lumbar vertebrae + 5 sacral vertebrae + 4 coccygeal vertebrae, which equals 33 vertebrae in total.