In interview, when the interviewer ask you why you left your previous work.what would you say?

I'm seeking a a new challenge and to grow my career and it was difficult to job search while working.

I believe that you should tell him the truth but don't ever criticize your boss ,it give a wrongfully impression.

If i have only the2 choices as you mention above than i will go with the2nd option of Looking for a better job...

Conceptually, I am looking for a new challenging opprotunity. I will never make any negative comments on on my previous employers.

I would tell the truth. Of course, I might be looking for a better opportunity. Or, I might have been laid off by my employer due to rightsizing, management handover,restructuring,  or other reasons. I should not say bad things about my previous employer, but telling the employer my real motive would demonstrate my integrity. Interviewers and recruiters are intelligent people and not only can they read between the lines but can also perform a background check including contacting the previous employer. This does not mean that I should be naive in presenting my real motive. On the contrary, I should disclose it cleverly making sure that the prospective employer would make only positive inferences. To conclude, I am against presenting a false or cliche motive or lying to the prospective employer, and in favor of putting forth the real reason behind leaving my previous work but in a smart and positive way without saying any thing bad about my previous employer.

To avail the batter career apportunity to grow up my capablities and skill. 

the answer is to have anew challenging career that can make my experience always in progress.

It is a tricky question but l would make everything look rosy.Most probably l would say l wanted to expose myself to the outer world by moving on.

An interview is always about YOU. so, i believe it's always better to avoid talking about your earlier / existing company / role / salary, etc. 

The best answers would be which cover the following -

1. project what you have learnt, skills aquired, the major challenges. And that you want to leverage these and grow more in a new challenging environment. 

2. Your ambition, your growth path. Your short & long term career plans aligned to the position you have applied for. 

If by any case, the candidate feels necessary to disclose financial reasons, he/she may discuss that. 

1.  Completion of the previous project.

2.  To build up my future career with your organization.

i will say what happend with me  without  any more or less 

i must be open book with him just to let him know the trues