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A. by B. at C. in D. on ( ) 3 Don39。t worry. He will return____. A. before long B. long before C. long long ago D. long ago Exercise ( ) 4 He arrived ___ Shanghai ___ 9: 30 ___ March 5. A. at。 in。 at B. to。 on。 at C. in。 on。 at D. in。 at。 on ( ) 5 Tom sits____the classroom while John sits____the room. A. in front of。 at back of B. in the front of。 at the back of C. in front of。 at the back of D. in the front of。 at back of Thank you