What is the output of the following command? for token in a b c; do echo -n ${token}; done

anbncn would only occur if the literal character 'n' were being output between values, but -n is an option flag consumed by echo to suppress newlines rather than a character that gets printed.

In each iteration of the loop, echo -n prints the current value of $token without appending a newline character. The three iterations print 'a', 'b', and 'c' consecutively with no separating whitespace or newlines, producing the single output string 'abc'.

$token$token$token would only appear if variable expansion were suppressed (e.g., inside single quotes), but bash expands $token to its current value on each iteration.

{a}{b}{c} would only appear if the variable reference were written with unrecognized brace syntax that bash left unexpanded, but both $token and ${token} are valid and bash expands them normally.

a b c with spaces would require either spaces being printed explicitly between values or separate echo calls that each append a newline; -n removes newlines and no space is ever printed.