Provided the input sentence, you're expected to write a question that involves event "frequency", which refers to how often an event is likely to be repeated. For example, "taking showers" typically occurs ~5 times a week, "going to Saturday market" usually happens every few weeks/months, etc. Don't create questions which have explicit mentions of answers in the text. Instead, it has to be implied from what is given. In other words, we want you to use "instinct" or "common sense". Also, the written questions are not required to have a single correct answer.

Let me give you an example: Sentence: Jack played basketball after school, after which he was very tired.
The answer to this example can be: How often does Jack play basketball?
Here is why: "Playing basketball" typically happens few times (1-7) per week, so it is a "frequency" question.

OK. solve this:
Sentence: Another unit was added on to the communal dwelling each time a marriage created a new family.
Answer:
How often are units added?