Which of the following was an issue of the progressive era

the options you provided were:

1) Recruitment

2) Security

3) Conservation

4) Financing

To give you and overview and some insight why or why not an option could apply, I'm heavily relying on wikipedia here, it's already well and short written.

unless marked otherwise, the source is

https://en.m.wikipedia.org/wiki/Progressive_Era

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"The Progressive Era (1896–1916) was a period of widespread social activism and political reform across the United States of America that spanned the 1890s to the 1920s."

"the Progressives were committed to changing and reforming every aspect of the state, society and economy."

-> so option 3 will not work I guess

"The purity of food, milk and drinking water became a high priority in the cities. At the state and national levels new food and drug laws strengthened urban efforts to guarantee the safety of the food system. The 1906 federal Pure Food and Drug Act, which was pushed by drug companies and providers of medical services, removed from the market patent medicines that had never been scientifically tested."

Option 2 serms nice for now

To be honest, I'm half an hour in by now and I can't say much for and against option 1 and 4 by now. But the don't seem overwhelmingly relevant. I would go with option 2, but also advice you to dive deeper into the topic if you want general understanding of US history.

I'll maybe look if crash course on YT got a good video for this topic, but so might you.

edit: they got one indeed

https://youtu.be/i0Q4zPR4G7M

video title: The Progressive Era: Crash Course US History #27

might be agreeing to participate ethically with other european nations in the slave trade

or notifying other european nations when taking possession   of african territories