... et Mexico (ne) va le payer!
(Sorry, couldn't have resisted for all the lavender of France.)
From the Notes Tips (Present 1):
A few defective impersonal verbs can only be used in impersonal statements and must be conjugated as third-person singular with il. Remember that il is a dummy subject and does not refer to a person.
Falloir means "to be necessary", and it often takes the form il faut + infinitive.
Il faut manger. — It is necessary to eat. / One must eat.
Il faut choisir. — It is necessary to choose. / One must choose.
Il faut can also be used transitively with a noun to indicate that it is needed.
Il faut du pain. — (Some) bread is needed.
In English "one" is generally altered to "we", hence the given answer.
If you wanted to specify that he has to do it, the best verb to use would be devoir - Il doit construire .....
Preceding falloir with an indirect object pronoun, example: Il lui faut construire ... allows you to specificity that "It is necessary for him to build .... "
That was helpful but then why not: It is necessary to build a higher wall.?? (and it is NOT by the way...)
"Il faut" doesn't translate to "he needs". It means that something needs to be done, but not by a particular person. If you wanted to say that someone, a "he" or "she", had to build something you would have to say "Il faut qu'il construise..." or "qu'elle construise..."
No, because the "il" doesn't refer to "he", it's an impersonal statement. I think you could call it a dummy subject. The expression is always "il faut" and it always means "it is necessary", or something equivalent.
While I think taller is a good adjective here Duo doesn't seem to agree. Note that the French sentence uses the indefinite article (un) but you've provided the English definite article (the).
I've reported that my translation "a higher wall must be built" was rejected in favour of "... has to be built". In UK English, my version is correct. Thanks.
I do think that in English your statement is more elegant. However, I don't think that DL wants people to change the sentence construction. You've changed the sentence from an active to a passive one.
"One need build a higher wall" seems correct to me. "One" is an example given, yet not accepted. In fact "one" is the first example given, and; proper American English.
I translated this as "you need to build a taller wall" . Does that make sense, with "you" being used in its general sense?
'It is necessary to build a higher wall' not accepted. Why is it wrong?
I understand il faut, the problem here is the inconsistent translation. It will randomly accept or reject, it is necessary, we must, you must, one must. You just never know what duo lingo will pull on you each time.