Visitors tour the 22nd China Beijing International High-Tech Expo in Beijing, capital of China. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors. (Photos: Xinhua)

Photo taken on Oct. 24, 2019 shows police robots displayed at the 22nd China Beijing International High-Tech Expo in Beijing, capital of China. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Photo taken on Oct. 24, 2019 shows engineering robots displayed at the 22nd China Beijing International High-Tech Expo in Beijing, capital of China. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Photo taken on Oct. 24, 2019 shows a hydrogen fuel cell car displayed at the 22nd China Beijing International High-Tech Expo in Beijing, capital of China. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Visitors taste desalinated seawater during the 22nd China Beijing International High-Tech Expo in Beijing, capital of China, Oct. 24, 2019. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

A staff member demonstrates a seawater desalination facility during the 22nd China Beijing International High-Tech Expo in Beijing, capital of China, Oct. 24, 2019. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

A visitor experiences the skiing training simulator during the 22nd China Beijing International High-Tech Expo in Beijing, capital of China, Oct. 24, 2019. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Visitors look at a holographic projecting device during the 22nd China Beijing International High-Tech Expo in Beijing, capital of China, Oct. 24, 2019. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Photo taken on Oct. 24, 2019 shows a neurosurgery robot displayed at the 22nd China Beijing International High-Tech Expo in Beijing, capital of China. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.

Visitors listen to introduction of a domestic water saving system during the 22nd China Beijing International High-Tech Expo in Beijing, capital of China, Oct. 24, 2019. The four-day expo opened here Thursday, drawing more than 1,200 exhibitors.