While I (play) in the field, I saw a dead cow.
playing
was playing
Correct
played
were playing
Explanation:
Correct Answer is: was playing
While এর পর verb থাকলে verb+ing হয়।
কিন্তু while এর পর subject থাকলে subject এর পর past continuous tense হয়।
এখানে while এর পর subject – `I` থাকার কারণে এর পরে continuous tense হিসেবে was playing বসবে।