Ok, so "Comment cela se fait-il?" by itself is the formal way of saying "How come?"
"Comment cela se fait-il que..." is the formal way of saying "How come...?" but since it is redundant the cela is often dropped.
"Comment se fait-il?" is never said by itself.
Have I understood correctly?
Further down in the discussion to this lesson:
Comment ça se fait ? (informal)
Comment cela se fait-il ? (formal)
Comment ça se fait que.... (informal)
Comment se fait-il que... (formal)
Incorrect usage: comment cela se fait que..., comment cela se fait-il que...
Ok, so "Comment cela se fait-il?" by itself is the formal way of saying "How come?"
"Comment cela se fait-il que..." is the formal way of saying "How come...?" but since it is redundant the cela is often dropped.
"Comment se fait-il?" is never said by itself.
Have I understood correctly?
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