Online Repository for accessing full academic articles and research papers completely free of charge is:

Correct option is A

ResearchGate is a professional network and online repository where researchers upload and share their work, including academic articles and research papers, often freely available. It serves as a valuable resource for free access to scholarly articles.

Information Booster:

• JSTOR, PubMed, and Google Books are also valuable resources for accessing academic content, but they may have limitations on free access, particularly without institutional access.
• ResearchGate allows for the sharing of full-text articles directly from the authors, making it unique compared to some other platforms that may require institutional subscriptions.

Additional Knowledge:

• ResearchGate has become one of the most widely used platforms for academics to collaborate, share research, and access articles for free, benefiting from the open-access movement.