托福考试

【单选题】A social system is （） of social relations that draws the behavior of its members toward the core values of the group. 
A. a complex network 
B. how a complex network 
C. a complex network and 
D. a network that is complex 

【单选题】 The eighteenth century witnessed the emergence of North American ports, particular Boston, New York, and Philadelphia, as major commercial centers within the British empire.

【单选题】 Ice crystals in a glacier tends to melt and recrystallize within a brief moment of travel on a downhill glide.

【单选题】 The hermit crab, a crustacean that uses an empty shell as a portable refuge to coverits soft abdomen, changes shellsas grows.

【单选题】 Electoral politics in the United States has been dominated by two political parties since the administer of George Washington.