Which out of the following statements is correct?

The correct answer is Option (1) → Seldom does she attend the theatre class.

An adverb is a word that tells how, when, where or how much something happens. It can also describe an adjective or another adverb, for example she sings sweetly, very hot.

Inversion after a negative adverb:

• Adverbs with a negative meaning, such as seldom, never, hardly, rarely, normally stand before the main verb: "She seldom attends ...".
• When such an adverb is put first for emphasis, the subject and the helping verb change places:
  • in the simple present, do/does is brought in.
  • pattern: Seldom + does + subject + base verb.
• This sentence: "Seldom does she attend the theatre class."

Why the Other Options are Incorrect?

Option 2: She is seldom attending the theatre class. — Incorrect. A habit is shown with the simple present. "Seldom" does not go with the continuous "is attending".

Option 3: Seldom she attends the theatre class. — Incorrect. With "seldom" at the start, the sentence must be inverted: "Seldom does she attend".

Option 4: She attends the theatre class seldom. — Incorrect. "Seldom" belongs before the main verb ("She seldom attends"). Left alone at the end of the sentence it sounds unnatural.

Contrast: normal order is "She seldom attends". With "seldom" first the order is inverted, "Seldom does she attend".