If you are following along with gcc on Linux and continuing to get linker errors even after adding -lfreetype, try passing it as the very last argument, e.g.
gcc `pkg-config --cflags freetype2` -Wall -Werror -o main main.c -lfreetype
> This whole “study” is based on data gathered through a “viral Facebook quiz” in which people provided self-assestments of their own skills and learning process.
The quiz (which you can take yourself at http://archive.gameswithwords.org/WhichEnglish/) measured syntactic competence with various tasks that were carefully tuned and based on prior peer-reviewed research [1, sec. 2.4]. At no point did quiz respondents provide self-assessments of their linguistic ability, beyond demographic information like identifying their native language and year of first exposure to English.
Historically inaccurate flags are used for the Soviet Union, Germany pre-1949, and Libya as well. It seems the creator chose to use the modern flag in all cases for consistency.