In the reading passage, it indicates that some people take optimistic attitude towards the replacement of traditional internal-combustion engines to hydrogen-based fuel-cell engines, based on three advantages.

In the reading passage, it indicates that some people take optimistic attitude towards the replacement of traditional internal-combustion engines to hydrogen-based fuel-cell engines, based on three advantages. However, in the lecture, the professor suggests that there are some challenges that have not been achieved, and she gives specific explanations. Firstly, the reading article expresses that hydrogen is easier to be obtained than gasoline or diesel fuel that is required by the internal-combustion engine. But, the lecturer argues that the hydrogen that can be used directly by the fuel-cell engine must be cooled down to -253 degrees and stay in pure liquid formation, which is difficult to achieve. Thus although many kinds of material could produce hydrogen, the technological difficulties could make it less attractive. Moreover, another benefit of using the fuel-cell engine would be environmental friendly, because the burning output of hydrogen is water rather than carbon dioxide which is polluted. Whereas the presenter said that the producing process of liquid hydrogen requires much fossil fuels, such as coals, which is harmful to environment. Finally, the reading passage argues that fuel-cell engines could save money because operating a fuel-cell engine could be more economical than operating a traditional internal-combustion one. Indeed, the professor tells that it cost enormous to product a fuel-cell engine since one composition of it a made by an extremely expensive metal named platinum, which have been found replaceable. Hence, even though burning hydrogen can save lots of money, the cost of manufacturing engines is unaffordable to normal users. Nowadays, it is still more economical to use internal-combustion engines.