Detailed Instructions: 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.
Q: Sentence: Construction on Hoover Dam (originally Boulder Dam, subsequently renamed for the president who authorized the project) began in 1931 in a canyon 45 miles (72 km) southeast of Las Vegas.
A:
How often did the construction workers work on the Hoover Dam?