一连
yī lián
in a row
in succession; running
one (一) + linked succession (连) = in a row, without interruption
Carts rolling one after another along a road — that unbroken chain of movement is exactly what 连 conveys. Pair it with 一 and you get the sense of things happening without a single gap between them.
他一连睡了三天。
tā yī lián shuì le sān tiān。
he slept for three days in a row.
她一连问了好几个问题，大家都没法回答。
tā yī lián wèn le hǎo jǐ gè wèn tí，dà jiā dōu méi fǎ huí dá。
she asked several questions in succession, and nobody could answer them.