Final answer:
The correct subjunctive form of the verb to complete the sentence is 'haya.'
Explanation:
The correct verb that best completes the sentence is 'haya'. The sentence should be: 'Es increíble que el parque de atracciones haya tantas montañas rusas.'
- Present subjunctive: 'Es increíble que el parque de atracciones haya tantas montañas rusas.'
Learn more about Subjunctive verb conjugation here:
https://brainly.com/question/49242964
