Explanation:

Russia has begun constructing its first strategic stealth bomber, capable of delivering nuclear weapons, under the Perspective Aviation Complex for Long-Range Aviation (PAK DA) programme. The strategic stealth bomber, the second 5th Generation combat aircraft from Russia after the Sukhoi Su-57 supersonic fighter, will eventually replace the currents set of strategic bombers Tupolev Tu 22, Tu-95 and Tu-160. The first test flight of the PAK DA bomber is likely to take place in late 2021 or early 2022. The bomber is expected to join the Russian Aerospace Force only by 2028 0r 2029 after rigorous testing and development. Hence option 3rd is correct.