30．We arrived at work in the morning and found that somebody into the office during the night.
(A)broke
(B)had broken
(C)has broken
(D)was breaking

我们在早晨到达工作地点是发现已经有人在前一天晚上闯进了办公室。两个时间点表示过去的过去，用过去完成时，选B。