三四天远远不够。（谓语动词用单数，道理同上）

Three or four days is far from enough.

哈里在后来的三四天接了每趟车。

Harry met every train for the next three or four days.

在随后的三四天里，11名证人将传唤来作证。

In the next three or four days, eleven witnesses will be called to testify.

克林顿就很少睡觉，他能一连活动三四天不休息。

Clinton hardly sleeps. He can campaign for three or four days straight without a break.