Step 1: Read the sentence carefully and note the time relationship between the two actions.
Step 2: The word “while” is used to show that one action was in progress when another action was completed.
Step 3: An action in progress in the past is expressed using the past continuous tense
(was/were + verb + ing).
Step 4: A completed action in the past is expressed using the simple past tense.
Step 5: Therefore, the correct combination is:
was watching (past continuous) and finished (simple past).
Step 6: The correct sentence is:
“While mom was watching the VCD I hired, I finished my assignment.”