例句與造句

1. fairly important covers have point-countable bases, weakly bases, k-networks, sequence-neighbourhood networks and so on . fairly important mappings have quotient s-mappings, closed s-mappings, open mappings, open-and-closed mappings, com-pact-and-open mappings, perfect mappings, countable bi-quotient mappings, compact mappings
   比較重要的覆蓋有點(diǎn)可數(shù)基，弱基，k網(wǎng)，序列鄰域網(wǎng)；比較重要的映射有商s映射，閉s映射，開映射，開閉映射，緊開映射，完備映射，可數(shù)雙商映射，緊映射。
2. It's difficult to find countable base in a sentence. 用countable base造句挺難的