The correct answer is: A. Apsara
Apsara is a research reactor located at the Bhabha Atomic Research Centre (BARC) in Trombay, India. It is a swimming pool-type reactor with a power of 10 MW. The reactor was built in the 1960s and has been used for a variety of research purposes, including studies of uranium heavy water lattice.
Zerlina is a research reactor located at the Institute of Physics and Nuclear Engineering (IPNE) in Bucharest, Romania. It is a pool-type reactor with a power of 1 MW. The reactor was built in the 1960s and has been used for a variety of research purposes, including studies of uranium heavy water lattice.
Dhruva is a research reactor located at the Indira Gandhi Centre for Atomic Research (IGCAR) in Kalpakkam, India. It is a heavy water moderated and cooled reactor with a power of 40 MW. The reactor was built in the 1980s and has been used for a variety of research purposes, including studies of uranium heavy water lattice.
Purnima-I is a research reactor located at the Bhabha Atomic Research Centre (BARC) in Trombay, India. It is a natural uranium moderated and cooled reactor with a power of 1 MW. The reactor was built in the 1960s and has been used for a variety of research purposes, including studies of uranium heavy water lattice.
Apsara is the only reactor among the options that is specifically designed for studies of uranium heavy water lattice. The other reactors are either multipurpose reactors or research reactors that are not specifically designed for studies of uranium heavy water lattice.