Answer
The Tamil population was left discontented by Sirimavo's Sinhalese nationalist policies because these policies favored the Sinhalese majority over the Tamil minority. For example, the Sinhalese Language Act of 1956 made Sinhala the only official language of Sri Lanka, which disadvantaged the Tamils who spoke Tamil as their first language. Sirimavo also supported the colonization of Tamil areas by Sinhalese people, which further marginalized the Tamils.