Given a scientific passage and an answer, generate a question for the given answer.

Passage: Only weak London dispersion forces hold molecules of nonpolar alkanes together in the liquid phase. Consequently, less energy is required to break these molecules away from the surface of the liquid and turn them into a vapor. The stronger hydrogen bonding between alcohol molecules means that more energy is required to convert the liquid to vapor, and boiling points are therefore high. Answer: stronger hydrogen bonding
What kind of bonding between alcohol molecules means that more energy is required to convert the liquid to vapor, and boiling points are therefore high?

Passage: Muscles cannot contract on their own. They need a stimulus from a nerve cell to "tell" them to contract. Let's say you decide to raise your hand in class. Your brain sends electrical messages to nerve cells, called motor neurons, in your arm and shoulder. The motor neurons, in turn, stimulate muscle fibers in your arm and shoulder to contract, causing your arm to rise. Involuntary contractions of cardiac and smooth muscles are also controlled by nerves. Answer: stimulus
What do muscles need to contract?

Passage: Scientists find answers using tests : When scientists want to answer a question, they search for evidence using experiments. An experiment is a test to see if their explanation is right or wrong. Evidence is made up of the observations a scientist makes during an experiment. To study the cause of death in the chimpanzees, scientists may give the chimps nutrients in the form of nuts, berries, and vitamins to see if they are dying from a lack of food. This test is the experiment. If fewer chimps die, then the experiment shows that the chimps may have died from not having enough food. This is the evidence. Answer: experiment
What is the term for a test to see if a scientific explanation is right or wrong?