I don't recall asking you anything.
Well that's simply not true. One of the most well-known trademarks in computers is "Apple".
When you see a pair of sunglasses that looks like this:
...you know they are Oakley brand sunglasses. Why? Because they have the letter "O" near the hinge, and that letter is a trademark of Oakley for eyewear.
When you see a magazine that looks like this:
You know it is Oprah Winfrey's magazine. Why? Because it has a large letter "O" on it, and that letter is a trademark of Oprah Winfrey for magazines.
When you see a retail website with this on it:
Then you know it is Overstock.com. Why? Because it has a large letter "O" on it, and that letter is a trademark of Overstock.com for retail online sales.
Single letters can certainly be trademarks for specific goods or services.
Nonsense. Can this one be a TM:
Continent+airlines?
Because "American Airlines" is also a very well-known trademark. It is fundamentally a descriptive term, but because they've been doing it since 1935 on a substantially exclusive basis, then that descriptive phrase has come to be solely associated with American Airlines. When someone says "American Airlines", they don't collectively mean United, Delta, Southwest, etc. - which are all American, and all airlines - they mean a specific airline which trades as American Airlines.
You are the last person on earth who should be giving others advice on avoiding legal problems, because you have no idea what you are talking about. Are you going to be held personally liable if your advice is wrong or bad? Is your license going to be in jeopardy if you give other people irresponsible advice based on your obvious ignorance of the subject?
A geographically descriptive term
MIGHT or
MIGHT NOT be a trademark based on a lot of specific facts.