Answer:
The relationship between confusion and growth in the text IS closely linked.
Explanation:
The subject and the verb of any sentence have to agree in person, or, simply put, if the subject is singular then the verb needs to be in the singular form, if the subject is in plural then the verb has to be in the plural form.
In this sentence, the subject is "the relationship" and that is singular, regardless of it showing the relationship between two things. So, the verb also has to be in singular form, which is IS instead of ARE.