试图和他讲道理没用；他从不听。

Trying to reason with him ___is ___no ___use; he never listens.

我们呼救，但没用，因为周围没人。

We called for help, but it ___was ___no ___use as no one was around.

没有合适的工具，这台设备将毫无用处。

Without proper tools, this equipment will ___be ___of ___no ___use.