My uncle arrived while I (cook) the dinner. (১৮তম শিক্ষক নিবন্ধন স্কুল: ২০২৪)

The correct answer is option (d) "was cooking." When two past actions are described — one ongoing and one interrupting — the ongoing action uses Past Continuous and the interrupting action uses Simple Past. Structure: While + Subject + Past Continuous, Subject + Simple Past. 'My uncle arrived' (Simple Past) interrupted 'I was cooking' (Past Continuous). Source: English Grammar in Use — Raymond Murphy.