例句與造句

1. For example, second countability and metrisability are hereditary properties.
2. Second countability is automatic for compact Riemann surfaces.
3. Notice how, to preserve properties such as local connectedness, second countability, local compactness etc & we require that the map be not only continuous but also open.
4. It's difficult to find second countability in a sentence. 用second countability造句挺難的