![A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)](http://www.ecns.cn/hd/2019/03/01/eb6063cfbc134d11834ce2704bc2fee9.jpg)
A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)
![A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)](http://www.ecns.cn/hd/2019/03/01/f39b0778fc384fe7a42d0f0d30fa9c2e.jpg)
A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)
![A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)](http://www.ecns.cn/hd/2019/03/01/f9b4db028f5d4598ad4c63ab0ef1cfb5.jpg)
A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)
![A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)](http://www.ecns.cn/hd/2019/03/01/003a05d0620f454c90b49fcbb451cbee.jpg)
A polar bear cub comes outside for the first time in the Copenhagen Zoo, Denmark, Feb. 28, 2019. (Photo/Agencies)