Now Playing: China subways inundated amid heavy flooding

Now Playing: DOJ charges 4 Chinese nationals with state-backed hacking

Now Playing: Creators of famous Sophia robot reveal AI robotics for children, elderly

Now Playing: Central China suffers devastating flash floods

Now Playing: US Olympic volleyball player reportedly tests positive for COVID-19

Now Playing: Japan Air Self-Defense Force aerobatics team draws Olympic rings in sky

Now Playing: Brisbane celebrates 2032 Olympics win with fireworks

Now Playing: NBA championship, asylum seekers and Eid al-Adha: World in Photos, July 21

Now Playing: ABC News Update: US volleyball player tests positive ahead of Olympics

Now Playing: Our favorite Prince George moments for his birthday

Now Playing: Hijab-wearing referee out to blaze trail at Olympics

Now Playing: ABC News Live: Johnson & Johnson shot may be less effective against delta variant

Now Playing: Olympic COVID-19 cases surge 155% in one week as opening ceremony nears

Now Playing: Russia targets Jehovah’s Witnesses with arrest, raiding of homes

Now Playing: Tokyo Olympics CEO doesn’t rule out canceling Games

Now Playing: ABC News Update: Jeff Bezos, Blue Origin crew land safely after spaceflight

Now Playing: Western Europe flooding, Blue Origin flight, and Dr. Fauci: World in Photos, July 20

Now Playing: Officials won’t rule out canceling Olympics at last minute