_____ country’s researchers have developed a new type of cooling vest for sports athletes which helps them to compete safely in sweltering summer conditions ?

1) USA
2) Russia
3) China
4) Japan

Explanation:
Japanese researchers from Hiroshima University have developed a new type of cooling vest for sports athletes which helps them to compete safely in sweltering summer conditions. The aim of the vest is to cool the athletes’ upper-body skin which can decrease heart rate and temperature of their neck and skin.This will help the athletes of the 2020 Tokyo Olympics will be held in the hot and humid Japanese summer where the ambient temperature is expected to be above 33 degrees Celsius,