他们正在调查肥胖症可能由病毒引起的假设。

They are investigating the ___hypothesis that obesity may be caused by a virus.

不幸的是，现实生活并不支持这一假设。

Unfortunately, real life does not back up this ___hypothesis.

在进行实验之前，科学家必须首先提出一个可检验的假设。

Before conducting the experiment, scientists must first formulate a testable ___hypothesis.