Ok, check this online Toefl test page,
Question: When did Mary ____ college?
B) graduate from (TOEFL thinks B is correct)
D) graduating from
I checked Oxford dictionary,
[intransitive, transitive] to get a degree, especially your first degree, from a university or college
graduate (in something) Only three students graduated in Czech studies last year.
graduate (from…) She graduated from Harvard this year.
He graduated from York with a degree in Psychology.
graduate something (North American English) She graduated college last year.
According to the dictionary, it seems that we use "graduate from" with specific universities or colleges & we use "graduate college" when we say "to graduate college" generally without knowing the specific one.
So, Why is "When did Mary graduate college?" considered wrong in TOEFL test?