Yes, there is a variety of things you can do to wear down the enamel. A few of the biggest things are: Drinking Coffee or soda, eating acidic foods and not brushing your teeth. Sadly you are not able to grow back your enamel after if it fully gone so it's best to protect your enamel as much as possible.
A 'Trend' is a large social influence if this is what you are talking about. Trends are something where one person does/wears it (usually a popular person everyone likes) and then everyone else starts doing it.
It would be C. Unused vitamin A is stored in fat cells of the body.
I think the best answer would be true bc its just true