--When did you come back from Beijing?

-- _________ the morning of April 18th．

A．At                B．In             C．On

?When did you come back from Beijing?

?_______ the morning of April 18th.

A. At

B. Within

C. On

D. In

?When did you come back from Beijing?

?________ the morning of April l8th.

A. At

B. Within

C. On

D. In

--- When did you come back from Beijing?

---________ the morning of April 18th.

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