How many people know that 16th, September of every year is the International Ozone Layer Protection Day?

有多少人知道，每年的九月十六日是国际臭氧层保护日？

youdao

How many people know that 16th, September of every year is the International Ozone Layer Protection Day?

有多少人知道，每年的九月十六日是国际臭氧层保护日？

youdao