20．It was four o'clock in the afternoon he and his grandpa reached the museum in Guanghan, an official warmly received them.
A. that; where
B. when; that
C. when; where
D. that; when
网友回答
A. that; where
B. when; that
(答案→)C. when; where
D. that; when
解析：可联系答.案.网客服索取。