A: What happened to Ann yesterday?
B: She was walking home when a man stole her bag.
In the first sentence, "happen" is in the past simple tense as it refers to an event that occurred in the past. In the second sentence, "walk" is in the past continuous tense as it describes an action that was ongoing at a specific point in the past, and "steal" is in the simple past tense as it describes a completed action.

A: Did you go out last night? B: No, I worked all day, so I stayed in and watched TV.
"Go" is in the simple past tense as it refers to a completed action that occurred in the past. "Worked," "stay," and "watched" are also in the simple past tense as they describe actions that were completed in the past.

A: Did you see your brother this morning?
B: No, he had already left the house by the time I woke up.
"See" is in the simple past tense as it refers to a specific time in the past. "Leave" is in the past perfect tense as it indicates that the action was completed before another past action (waking up). "Wake" is in the simple past tense as it describes a completed action in the past.

A: Why were you running when I saw you yesterday?
B: Oh, I was chatting to a friend for ages when I realized I was late for school.
"Run" is in the past continuous tense as it describes an ongoing action at a specific point in the past. "See" is in the simple past tense as it refers to a specific time in the past. "Chat," and "realize" are in the past continuous tense as they describe ongoing actions in the past.

A: I called you at 10 o'clock yesterday morning.
B: Oh, we probably didn't hear the phone.
"Call" is in the simple past tense as it refers to a specific action in the past. "Hear" is in the simple past tense as it describes a specific action in the past.