By saying "but no one seems quite sure which way happiness ran" (Line 2, Para. 1), the author suggests that the American are not quite sure of ______.

A．At the office
B．In the street
C．In a classroom
D．In a restaurant

A．The weather gets hotter.
B．Telegraph wires stand still.
C．Swallows sit on telegraph wires.
D．People find the mystery of migration