main.c: In function ‘main’:
main.c:4:10: error: ‘This’ undeclared (first use in this function)
    4 |   printf(This sentence will produce an error.);
      |          ^~~~
main.c:4:10: note: each undeclared identifier is reported only once for each function it appears in
main.c:4:14: error: expected ‘)’ before ‘sentence’
    4 |   printf(This sentence will produce an error.);
      |         ~    ^~~~~~~~~
      |              )