Photo taken on May 21, 2021 shows an exterior view of the 12th Expo Central China in Taiyuan City of north China's Shanxi Province. The 12th Expo Central China kicked off here on Friday. (Photos; Xinhua/Yang Chenguang)

A visitor takes picture of exhibits displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

An exhibitor (1st R) introduces tea products to visitors at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch a helicopter displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

People visit the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch exhibits displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch exhibits displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch exhibits displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

An exhibitor introduces helicopter products to visitors at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch a helicopter displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Artists play musical instruments at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

An exhibitor (1st L) introduces reflex bow products to visitors at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

People visit the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Visitors watch exhibits displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.

Photo taken on May 21, 2021 shows a magnetic-controlled, capsule-shaped gastroscope displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province. The 12th Expo Central China kicked off here on Friday.

Visitors watch a fire-fighting robot displayed at the 12th Expo Central China in Taiyuan City of north China's Shanxi Province, May 21, 2021. The 12th Expo Central China kicked off here on Friday.