Question

はるか

2行目のcan beの意味はなんですか？
また、3行目最後の「in」はなぜ、「on」では無いのでしょうか？

David Greybeard first showed me lhow ( 1) the distinction between animals
and humans can be.」 Forty years ago I befriended David, a chimpanzee, during
my first field trip to Gombe in Tanzania. One day I offered/ him/a (nut in my
open palm. He looked directly into my eyes, took the nut out of my hand and
5 dropped it. At the same moment he gently squeezed my hand as if to say, I
+ 1
TTO11