Foreign language study is not mandatory in U.S. schools, but Lois has a college degree, and most colleges require two years of foreign language study in high school and either a course in college or a competency test to get out of the college course. That means that at some point Lois had at least some knowledge of a foreign language. Given the time she was in school, it was probably Spanish, French, or German. I'm sure it's pretty rusty by now if she hasn't intentionally kept up with it.
