You will be given a definition of a task first, then some input of the task.
In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.

As of 2016, there are 3 hydrogen cars publicly available in select markets: the Toyota Mirai, the Hyundai ix35 FCEV, and the Honda Clarity. Several other companies are working to develop hydrogen cars. As of 2014, 95% of hydrogen is made from natural gas. It can be produced using renewable sources, but that is an expensive process. Integrated wind-to-hydrogen (power-to-gas) plants, using electrolysis of water, are exploring technologies to deliver costs low enough, and quantities great enough, to compete with hydrogen production using natural gas. The drawbacks of hydrogen use are high carbon emissions intensity when produced from natural gas, capital cost burden, low energy content per unit volume, production and compression of hydrogen, and the large investment in infrastructure that would be required to fuel vehicles.
Output:
where do scientists hope to get hydrogen to use in cars