The tone of the passage can most probably be described as

A．Migration exerts a great impact on population change.
B．Migration contributes to mankind's progress.
C．Migration brings about desirable and undesirable effects.
D．Migration may not be accompanied by human conflicts.

A．they both benefited from Italian sponsors.
B．they were explorers in their own ways.
C．they obtained overseas sponsorship.
D．they got a warm reception in America.