Of the options that you have given us here, the best answer is #2.   Women in many countries, including the United States, the United Kingdom, Germany, and France, were brought into the work force to help fill the need for increased manufacturing.  Their work was critical because so many men were off fighting and because there was such a great need for war materiel.

Of course, this does not mean that women kept their place in the work force for long after the war ended.  The war did not have that kind of a long-lasting impact.  However, for as long as the war lasted, it brought large numbers of women into the work force.