题目选项分析

A study has recently shown that happier employees are more productive. Employees at Davis Industries are more productive over the course of the business day than those at Saturnine Corporation. Therefore, we can conclude that Davis Industries' employees must be happier than those at Saturnine Corp.

The argument is most vulnerable to which of the following criticisms?

【选项】The evidence it uses is simply a paraphrase of its main conclusion.