Please choose the correct answer to the question: After observing several dogs running, students ask the following question: Do dogs with long hair run faster than dogs with short hair? How can the students best answer their question?

Answer1: record the weights and heights of many dogs Answer2: measure the speeds and hair lengths of many dogs Answer3: research to find the type of dog with the longest hair Answer4: race one long-haired dog against one short-haired dog

Answer format: answer1/answer2/answer3/answer4