Explanation:

- Option 1: Chehllum

- Chehllum, also known as Arba'een, is a religious observance in Islam. It commemorates the end of the 40-day mourning period after the Day of Ashura.

- Option 2: Chitragupta Pooja

- This festival is dedicated to the worship of Chitragupta, the Hindu god who keeps records of actions and deeds. It's not related to the Sun God.

- Option 3: Chhath Pooja

- Chhath Pooja is indeed dedicated to the Sun God (Surya) and his wife Usha. It is celebrated to express gratitude and seek their blessings for health and prosperity.

- Option 4: Basant Panchami

- Basant Panchami marks the arrival of spring and is primarily dedicated to Saraswati, the goddess of knowledge, rather than the Sun God.