关口

shǒu wèi guān kǒu

守卫关口

guard a pass

chóng jiàn guān kǒu

重建关口

rebuild a pass

xiá zhǎi de guān kǒu

狭窄的关口

narrow pass

jiě jué wèn tí de guān kǒu

解决问题的关口

key point of solving a problem

kē jì tū pò de guān kǒu

科技突破的关口

key point of technological breakthrough