You may say you didn\'t fit into their company cultural, usually if u answer that, they will ask u what sort of culture u will fit in.
That depends on the company u going to interview, if it is a MNC, u can say you like it more dynamic, more international exposure. If it\'s a local company that u r interviewing, you can say you can want to change the environment becoz the pervious job itself doesn\'t not fit to the JD that was discussed with you on your interview, and you can elaborate a bit more.
I hope this help.
N.B: I\'m a HR Director in a listed company for many years, mainly responsible for APAC recruitment and over look the full spectrum of all HR related matter for APAC.