Please choose the correct answer to the question: Hydrogen is located on the left side of the periodic table in the same column as the alkali metals, but it has characteristics of a nonmetal. Which of the following is a physical property of hydrogen?

Answer1: Hydrogen can bond to itself. Answer2: Hydrogen makes positive ions. Answer3: Hydrogen is a gas at room temperature. Answer4: Hydrogen is combustible.

Answer format: answer1/answer2/answer3/answer4