托福考试

【单选题】
单项选择

【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】 The membrane surrounding a single-celled animal or plant or any individual cellin a multicellular organism is important in the respiratory and nutritionally processes of that cell.

【单选题】 What did researchers discover in the study of honeybees discussed in paragraph 2
A．( Bees are able to travel at greater speeds than scientists thought
B．( The bees could travel 25% farther than scientists expected
C．( The bees were able to determine in advance where scientists would place their food
D．( Changing the location of food caused bees to decrease their dance activity

【单选题】 The invention of reinforced concrete, plate glass, and steel in the mid-1800's (was enabled) architects(to design) and build (extremely tall) constructions, (or) "skyscrapers."
A．was enabled
B．to design
C．extremely tall
D．or