我怀疑他帮忙纯粹是出于善意。

I suspect he helped ___purely out of kindness.

我们必须完全靠自己组织这些活动。

We had to organize the activities ___purely by ourselves.

这个装饰纯粹是观赏性的，没有任何实际用途。

The decoration is ___purely ornamental; it serves no practical purpose.