Before world war ii, women had served in war as combat soldiers. air traffic controllers. officers. nurses.

Before World War II, women had served in war as nurses (option 4). Women have contributed in war in many diverse ways, some of them are, for example, cooking and doing laundry. But the most important role they were assigned, since mid 19th century, was, o course, nursing.

It wasn't until World War II that women began taking up more military involved roles, such as serving in combat roles. This was due to World War II being a global conflict much larger than expected. It was considered an absolute urgency, and more people were needed in combat, that's why women started to get more involved.

a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :

( a ) be more interested in objective data and statistics.

d. china

good luck

d is the best choice