Translation:It is important to call the police immediately.
This is why.....
Il est + adjective
C'est + noun
I was marked wrong for using "call for police" instead of "call police". Any thoughts as to why?
That was what I thought - but it was not accepted. Shouldn't the adverb follow the verb, well, immediately?
I think you are inclined to use "à" because it is tempting to translate "important to call" literally... in this case though, "to" in "to call" is not a preposition, but simply an indication of infinitive form of the verb "to call".
Impersonal expressions, such as "il est important...", "il est bon", "il est est dificile...", etc, are always followed by one of two things:
"que ..." + a subordinate clause or a preposition and an infinitive/subjunctive.
Example using que: "il est important qu'il le fasse"-- it is important that he does it.
When it comes to prepositions, either "de" or "à" are used, depending on the context. When the subject of the expression is not replacing a specific person/place/thing (i.e. a dummy subject), we have to use "de". When the subject of the expression is replacing a specific person/place/thing (i.e. a real subject), "à" is used.
Here is an example:
This is a fact. It is important to understand this fact.----> C'est un fait. Il est important de le comprendre. VS. This is a fact. It (the fact) is important to understand.----> C'est un fait. Il est important à comprendre.
Hope this helps:)
I have noticed as a learner that a good way to develop a feel for this and other rules that seem alien at first is that they largely rely on a balance of specificity, ie a noun is more specific. And thus a less specific preposition is produced alongside it in expression. Just a bit of aesthetics :)