Her dream of having a home; the insurance money; Ruth's pregnancy.
In "A Raisin in the Sun," we meet the Youngers, an African American family living on the South Side of Chicago during the 1950s. The family's matriarch, Mama, always dreamed of buying a house with her husband, but was not able to. An opportunity arises when, after his death, the family receives his death insurance payment. Each member of the family has a different opinion regarding what the money should be used for. However, upon finding out that Ruth, Mama's daughter-in-law, is pregnant, Mama decides that a house is the way to improve their sitation, and decides to buy one in a predominantly white neighbourhood.
Her family fighting ~ APEX
The answer is: b. Ruth's pregnancy
After hearing about the pregnancy, Mama automatically think that the family need a space to live in. This influence her to buy the house. Put problems arise because mama did not tell them that she bought the house using Walter's insurance money.