Exp) Option b is the correct answer.

Microgravity research involves studying the behavior of physical, chemical, and biological systems in environments where gravity is significantly weaker than on Earth. Such research is crucial for advancing our understanding in various fields, including human physiology, material science, and space agriculture.

Option I is correct. The Axiom-4 (Ax-4) mission is a collaborative effort involving Axiom Space, NASA, ESA, and ISRO. Scheduled for launch in June 2025, this mission will send a crew to the International Space Station (ISS). Notably, Group Captain Shubhanshu Shukla, an Indian Air Force test pilot, will be part of this mission. During the mission, the crew will conduct over 25 experiments focusing on various aspects of microgravity, including:

•       Human health: Studying the effects of microgravity on the human body, such as muscle atrophy and cognitive functions.
•       Space agriculture: Investigating the growth of crops like green gram (moong) and fenugreek (methi) in microgravity conditions.
•       Biotechnology: Examining microbial adaptation and other biological processes in space.

These experiments aim to enhance our understanding of living systems in space and support future long-duration missions.

Option II is correct. The Space Docking Experiment (SpaDeX) is an initiative by ISRO to demonstrate autonomous docking capabilities between two satellites in orbit. While the primary objective is to validate docking technologies, the mission also supports microgravity research through the PSLV Orbital Experimental Module (POEM-4). This module utilizes the spent fourth stage of the PSLV rocket as an orbital platform for conducting experiments in microgravity, including:

•       Plant growth studies: Observing the germination and growth of seeds in microgravity to understand plant behavior in space.
•       Radiation environment measurements: Monitoring space radiation levels to assess their impact on biological systems.

These experiments provide valuable insights into conducting scientific research in microgravity environments.

Option III is incorrect. Gaganyaan is India’s ambitious human spaceflight program, aiming to send a crew of three astronauts into a 400 km orbit for a three-day mission. 

As per the UPSC CSE 2025 prelims answer key Only 2 options are correct, so most probably Option III i.e. Gaganyaan would not encourage and support microgravity research as the primary focus is the Human spaceflight program.

Along with Ganganyaan, building of national space-based facility such as the Bharatiya Antariksh Station was approved. It will boost microgravity based scientific research & technology development activities. This will lead to technological spin-offs and encourage innovations in key areas of research and development.

Sources: https://www.axiomspace.com/missions/ax4 ; https://www.pib.gov.in/PressReleasePage.aspx?PRID=2088569 ; https://www.isro.gov.in/ISRO-ESA_collaboration_in_microgravity_research_in_upcoming_Axiom-4_Mission.html#:~:text=Indian%20Human%20Space%20Program%2C%20Gaganyaan,well%20as%20joint%20international%20efforts. ;