Silly me, I bought a telephoto lens after Safari trip …
I did quite a lot of research, and my choice was Canon EF 70-300mm f/4.0-5.6 L IS USM.
But finally, I was persuaded by the sales to buy another telephoto lens.
Canon EF 70-200mm f/2.8L IS II USM
200mm is definitely not enough for shooting wild animals … (prepare for the future), and of course EF 100-400mm f/4.5-5.6L IS II USM is the best for Safari photo, but it is too expensive and too heavy.
This lens is compatible with Extender EF 1.4x III (Extender EF 2x III is also available) which the the focal length can be increased by a factor of 1.4x. Some people said that using Extender EF 1.4x will reduce the image quality, probably yes, but honestly I can’t tell the difference.
The 1.4x Extender will also decrease the maximum aperture, so I think I will only consider 1.4x but not 2x.