1. What does the passage mainly discuss? (A) Philadelphia's agriculture importance (B) Philadelphia's development as a marketing center (C) The sale of imported goods in Philadelphia (D) The administration of the city of Philadelphia

47. According to paragraph 2, which of the following has made the study of pheromones difficult? (A) Pheromones cannot be easily reproduced in chemical laboratories. (B) Existing technology cannot fully explore the properties of pheromones. (C) Pheromones are highly volatile. (D) Pheromone signals are constantly changing.

1. What does the passage mainly discuss? (A) Philadelphia's agriculture importance (B) Philadelphia's development as a marketing center (C) The sale of imported goods in Philadelphia (D) The administration of the city of Philadelphia

其他試題

1. What does the passage mainly discuss?
(A) Philadelphia's agriculture importance
(B) Philadelphia's development as a marketing center
(C) The sale of imported goods in Philadelphia
(D) The administration of the city of Philadelphia