Yep, same problem and I have found out why.
I went to science-quizzes directory and see that there is still only two files and biology.txt does not exists!
ssssoooo, i created it by myself, added, commited and BAM! Commands in instruction worked well in my bash, but exercise still not passed =( maybe cuz lines in bash are not the same as in example in instruction.
so i think it is some bug in excercise.
upd: passed by closing bash and starting new session in each excersice.