他的结论建立在未经证实的假设之上，缺乏可靠证据支持。

His conclusion was built on unfounded ___suppositions without solid evidence to back it up.

科学家们基于现有数据做出了一些假设，但尚未得到证实。

The scientists made several ___suppositions based on the available data, but they haven't been proven yet.