Both "and" and "or" can be correct in this sentence, depending on what you want to express:
1. "They don't know how to be strong and brave."
- This means they don't know how to be both strong and brave at the same time. It implies they lack knowledge or ability to embody both qualities together.
2. "They don't know how to be strong or brave."
- This means they don't know how to be either strong or brave individually. It implies they lack the ability to embody either of these qualities.
Key Difference:
- Use "and" if you mean both together.
- Use "or" if you mean either one or the other.
In negative sentences, "or" is more common when listing alternatives, but both are grammatically correct depending on the intended meaning đ