What Was the "Gentlemen's Agreement of 1907

What was the "Gentlemen's Agreement of 1907"?

A) a U.S. congressional act that barred further immigration from China
B) a series of diplomatic accords between Japan and the United States that barred new immigration
C) a presidential order that rounded up two-thirds of Japanese American citizens and sent them to incarceration centers at the onset of World War II
D) a policy instituted after the Vietnam War whereby Vietnamese citizens were housed in refugee camps and supported by the U.S. government