am selected interview.they tell chose QC Or QA…what is the best department
I would suggest you to chose QC (Quality Control) department. This is beacause QA is responsible for establishing Quality Management System across the organization / Manufacturing plant. and ensuring overall compliance to GMP, GLP, GXP requirements through conducting internal audits of different departments (QC, Warehouse, Production, Utilities etc.) and through documents review.
In QC you will learn various componenets of GMP, GLP such as quality requirements of raw materials, Intermediates, Packaging materials, In-process material. controls through anlysis & testing, similarly final products quality attributes through analysis of final products as per specifications, Vendors & suppliers evaluation, understanding calibration, Qualification (IQ, OQ, PQ) & validation aspects, QC documentation in greater details.
In Quality Assurance you need to gain in-depth knowledge on these aspects and must know all the aspects of GMP, GLP, & Good documentation practices (Data Integrity). Therefore, after gaining sufficient knowledge on these aspects in Quality Control you can subsequently shift to QA department so that you will be able work in QA satisfactorily. Without having this basic knowledge it would be somewhat difficult to understand GXP apects which are very important to work in QA.
(This is appliable when you do not have previous experience of working in QA)