题目选项分析

Although a new fat-substitute-based oil on the market would help many people lose weight, dieters should be cautious when using it. The product has been approved by the government, but in laboratory studies, several individuals experienced stomach distress after eating food containing the oil.

The bolded phrases play which of the following roles in the passage above?

【选项】The first phrase expresses a causal relationship and the second phrase is evidence for the causal relationship.