Either a past participle would fit in the blank to form present perfect tense or a present participle to form present perfect continuous tense. So, noun 'enchantment' (a feeling of great pleasure), verb/adjective 'interested' and verbs 'beguile' (charm) and 'captivate' (charm) are eliminated. Thus, 'fascinating' is the apt choice which would convey that aurora borealis have been charming people for years.
Hence, option (e) is correct.
NOTE:
Participle: A word formed from a verb (e.g. going, gone, being, been) and used as an adjective (e.g. working woman, burnt toast) or a noun (e.g. good breeding). In English participles are also used to make compound verb forms (e.g. is going, has been). Consider the sentences given below:
Dancing at the party, the women fell on the ground.
Encouraged by her parents, Rita went on to pursue her passion.
The highlighted word in the first sentence is of the form Verb + ing and is used as a present participle. It is used to denote an action that is going on or incomplete or imperfect.
The highlighted word in the second sentence is of the form verb + ed. It is used as a past participle. It denotes completed action or state of the thing spoken of.
A past participle ends with the following: -ed, -d, -t, -en, or -n.
One should take great care and never get confused between a gerund and present participle. They use the same forms but perform different functions: a gerund is a verbal noun, while a present participle is a verbal adjective.