这种持续的高强度工作压力让人无法忍受。

The constant high-pressure workload became ___unsupportable.

她的主张站不住脚，因为没有确凿的事实依据。

Her claim was ___unsupportable because there were no solid facts to back it up.

这个项目的运营成本太高，根本无法维持。

The operating costs of this project are ___unsustainable for any extended period.