Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: Since four out of five of people have back pain , often lower back pain , sometime in their life , we should know what causes it and how to avoid it . Causes Of Lower Back Pain As we get older , our bodies tend to lose their muscle elasticity and tone , as well as bone strength . The discs in our spine lose fluid and flexibility , and they ca n't cushion the vertebrae as well anymore .

Question: What type of pain or injury is the narrator discussing .
None of the above choices .
Lower back pain.