Answer:
What I see in the placard.
A group of women not of Caucasian descent sitting and standing around a white woman who seems to be teaching them from a book she has in front of her.
Cause of New Imperialism ⇒ Spreading Christianity and Perceived obligation to civilize the locals.
During the time of New Imperialism, European countries were not as religious as they once were but were still quite religious to the point that they felt it was their sacred duty to spread Christianity around the world. They colonized parts of Africa and Asia to ensure the message spread with more ease.
Europeans also felt it was their moral obligation as a superior race to try to civilize Africans and Asians by teaching them various things that were considered civilized.
This is what the woman here seems to be doing. She is either teaching them about Christianity or other things that were considered civilized by Europeans at the time.