Final answer:
The phrase 'No creo que' triggers the use of the subjunctive mood in Spanish, expressing doubt or hypothetical situations rather than certain facts.
Step-by-step explanation:
The phrase 'No creo que' is typically followed by the subjunctive mood because it expresses doubt or disbelief, which is a trigger for the subjunctive in Spanish. The subjunctive mood is used to express wishes, suggestions, or conditions that are not factual or are hypothetical. When you say 'No creo que,' what follows will generally be a statement that the speaker does not believe to be true or certain. For example, 'No creo que él tenga razón' translates to 'I don't think that he is right,' where 'tenga' is the subjunctive form of the verb 'tener'.