✔ 最佳答案
I have other way to describing that meaning.
1. Can = 能夠......是自然的,與生俱來的,是一種本能,母須經過訓練/學習.
2. could =( past tense ) 是之前在著的.經驗過的.就用could.
例 : Can you do that? =是 (未知你有能力否).你能做嗎?
......Could you do that?=是(已知你做過).你可以(再)做嗎?
3. be able [ to......]是要經過學習/訓練,懷著才能,才藝,才華,才有能力去幹.