9. _______ a cold morning in June, I saw a stranger walking around the house

9. _______ a cold morning in June, I saw a stranger walking around the house
9. _______ a cold morning in June, I saw a stranger walking around the house

9. _______ a cold morning in June, I saw a stranger walking around the house
on
因为morning前有形容词修饰将其具体化了,否则一般用in