Answer:
English is considered the Lingua Franca. A Lingua Franca (also can be identified as a common language) is a language that is adopted as a common language between speakers whose native languages are different. That means, for example, if there is an international business meeting between Germany and Japan, the people will most likely speak English.
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Answer:
I would think that this means that he can use his happiness to hide his true face and emotions. He can put the mask on and appear happy to others, when really he is not. This acts like a mask because a mask makes your face look like something it isn't. Like on Halloween when you dress up, wearing a mask makes you look like what you desire to look like, not what you really are.