Please,
Which one can I use for grammar U.S.?
Thanks 
traveled = US English
travelled = UK English
It’s not a question of grammar but just spelling.[YSaerTTEW443543]
TOEIC listening, talks: Leaving a voice message for a potential Internet business partner[YSaerTTEW443543]
THANKS,
I trought was grammar because took about verb. 
Again, thank you for you attention and please correct me always!
Well to be a bit more specific it IS a grammar thing but one of those grammar mistakes which after a while just stuck in modern English. This time, in British English only. =] Here’s a simple copy paste which kinda explains it a bit.
"When adding -ing and -ed to verbs, we sometimes double the consonant beforehand. People are often confused with ‘travelled/traveled’, ‘benefitted/benefited’, ‘focussed/focused’ and ‘targetted/targeted’. This tip answers some of those queries.
The official requirements are that we ‘double a single consonant letter at the end of any base where the preceding vowel is spelled with a single letter and stressed’. …
Examples:
word present participle past participle
bar barring barred
beg begging begged
occur occurring occurred
permit permitting permitted
patrol patrolling patrolled
It is true to say that there is usually no doubling when the preceding vowel is unstressed (‘enter’ becomes ‘entering/entered’; ‘visit’ becomes ‘visiting/visited’) or when the preceding vowel is written with two letters (‘tread’ becomes ‘treading/treaded’).
Travel
However, with some final consonants, even in cases when the preceding vowel is unstressed (so you would think that there would be no doubling), doubling does occur in standard received British English (but is not favoured in American English), so ‘travel’ becomes ‘travelling/travelled’. Others in this grammatical group (verbs ending in an unstressed vowel, followed by the letter ‘l’) are ‘cancel’, ‘counsel’, ‘dial’, ‘model’, ‘parallel’ and ‘signal’.
The whole article can be found here:
future-perfect.co.uk/grammar … aveled.asp
There’s also a pretty cool English spelling comparison chart here:
en.wikipedia.org/wiki/Wikipedia: … ison_chart
-Chilly