Final answer:
The correct verb is 'hablando' and it means 'speaking'.
Step-by-step explanation:
The correct verb to complete the sentence is 'hablando'.
'Los turistas están hablando en español' translates to 'The tourists are speaking in Spanish'. When talking about an ongoing action, the verb 'estar' is used in its present progressive form ('están') followed by the gerund form of the verb ('hablando'). This expresses that the tourists are currently engaged in the activity of speaking in Spanish.
Learn more about Verb conjugation in Spanish