3 I was cooking ..... Angela was watching TV.

Step 1: Determine the relationship between the two clauses. Both actions, cooking and watching TV, were happening at the same time.
Step 2: Select the appropriate conjunction for simultaneous actions. 'While' or 'as' are suitable.
Step 3: Evaluate the given options. Option A, 'while', correctly indicates simultaneous actions. Option B, 'after', and C, 'just as', do not fit as well.
Answer: while