In the first activity, the command

$\frac{}{?}$ cpp$-$hello$-$world$ a$.$out

was intended to run the program named a$.$out, but did not work due to an error. What is the best explanation for the error? usage error: the filename needs to be preceded with $./,$ so the command is

configuration error: you must move to the home directory before running a$.$out usage error: the command needs an additional $-$o argument, so the command is

configuration error: you must always execute a "git push" command before running a$.$out