In one exercise the português translation for - “ The topic is difficult, but the questions are easy”
is
“ A matéria é difícil, mas as perguntas são fáceis”
Why are we using matéria vs tópico in this, while there is a choice for tópico in the excercise?
@mohan.ajay, tópico is an acceptable direct translation for “subject” or “topic”, but not a very idiomatic one when we’re talking about school and the topics that come up in school exams. Matéria (not tópico) is our word of choice to talk about the topics that students learn about and are tested on within a certain class. This is not to be confused with disciplina, which is our high-level term for each subject.
For example, History would be a disciplina. Within it, the topics of the Renaissance or Ancient Egypt would be matéria that the students would need to study.
In the exercise you mentioned, the option that includes the word tópico is visibly incorrect for a different reason 