单选题 War and famine have forced people in the region to ________ from their homes to other countries.

单选题 The remote Pacific island has only been visited by tourists ______ rare occasions.

单选题 These books shed light ______ the political and social life of ancient Chinese society.

单选题 This river used to be an ________ leading into London.

单选题 While some lost cities were discovered after years of searches, some others were found _____ .

单选题 Joint efforts by all countries are needed to prevent natural resources from being .

单选题 The historians have to read extensively ______ search of historical clues.

单选题 The cultural exchange between China and other countries is more ________ than before.

单选题 ______ its heyday, the hotel was mostly occupied by traveling salesmen in the 1920s and 1930s.