The grammar book I'm studying translates the following sentence like this:

> 
> English: The death is certain, uncertain is the day of death.
> 
> 
> Latin: Mors certa, dies mortis incerta est.
> 
> 
> 

However, I'd translate it like this:

> 
> Mors certa est, mortis dies incerta est.
> 
> 
> 

Is it just a question of style, or is it a rule to omit the verb?