YOU SAID:
he could swallow it whole
INTO JAPANESE
彼はそれを丸ごと飲み込むことができた
BACK INTO ENGLISH
He was able to swallow it whole
INTO JAPANESE
彼はそれを丸ごと飲み込むことができました
BACK INTO ENGLISH
He was able to swallow it whole
You've done this before, haven't you.