Final answer:
The statement that the marketplace remained completely closed to Black women during World War II in California war industries is not true. Some managed to secure jobs in the defense industry and challenged segregation by insisting on black supervisors and collective action against mistreatment.
Step-by-step explanation:
Among the statements regarding women workers in the California war industries during World War II, the one that is not true is that for the most part, the marketplace remained entirely closed to Black women. While there were significant limitations and discrimination, some Black women were able to secure government jobs or positions as laborers in the defense industry, as monitored by the War Industries Board. Furthermore, they were sometimes able to secure black supervisors and sought collective actions in mistreatment cases.
Despite facing segregation and often being given the hardest machines to operate, industrial work was a welcomed change from domestic service for those who did secure positions. It's important to recognize that while there were barriers, the absolute statement that the marketplace remained closed to Black women is not accurate; there were instances where Black women participated in the war industry, albeit in a limited and often segregated capacity.