Recent research suggests that there is a link between and low-back pain.

smoking

Explanation:

Smoking. Nicotine restricts blood flow to the disks that cushion your vertebrae and increases the rate of degeneration, Shin says. This loss of cushioning can cause back pain. ... Additionally, coughing from heavy smoking can cause back pain.

for me i have felt invisible when i was clearly struggling,or,i made a great achievement ,and,nobody took to notice me either because they just didn't see it,or,people just turned their back on me.i can see a person being invisible by choice,or,without choice like i did.the people who are invisible by choice don't try to talk to people,don't try to make friends,and,keep to themselves.i haven't been one of those people so i couldn't give you a reason.

hope this and can i get bainliest my dude : d

c. will be your answer sorry if im wrong tho