After a thorough review of literaturea.All of themb.Certain claims and statements are revisitedc.Research questions and objectives changed.Existing knowledge is acknowledged

It seems like you're asking about the steps involved in a literature review. Here's a step-by-step breakdown:

1. Thorough Review of Literature: This is the first step where you read and understand the existing research and theories related to your topic. You identify key themes, debates, and gaps in the existing literature.

2. Acknowledging Existing Knowledge: After understanding the existing literature, you acknowledge it in your research. This means you refer to it, showing how your research builds on it, fills gaps, or offers a new perspective.

3. Revisiting Certain Claims and Statements: As you delve deeper into your research, you may find that some claims or statements made in the existing literature need to be revisited. This could be because they are outdated, have been disproved by later research, or because you have a different interpretation.

4. Changing Research Questions and Objectives: Based on your review of the literature and the gaps you've identified, you may need to revise your research questions and objectives. This is a normal part of the research process - as you learn more about your topic, your understanding of what needs to be investigated can change.

So, the answer to your question would be "All of them" as all these steps are part of the literature review process.