Question

who has the sole right to dissolve the lok sabha?

Answer 1

The President has the sole right to dissolve lok sabha

Answer 2

The term of Lok Sabha is five years. When the term is over, the President of India can dissolve Lok Sabha. He does not need the Prime Minister's advice for the same.
When the term, dissolution of Parliament is used, it only means the Lok Sabha, the House of the People, the Lower House of Parliament. Parliament comprises the President, Lok Sabha, and Rajya Sabha, the Council of States, the Upper House.