groundless

这一反对意见是毫无根据的，缺乏支持。

The objection is ___groundless, lacking support.

他对我的指责完全没有依据。

His accusations against me were completely ___groundless.

她的担忧是毫无根据的，因为没有任何迹象表明会有问题。

Her worries were ___groundless as there were no signs of any problems.