⎕DL Delay

The monadic system function ⎕DL delays execution for not less than the number of seconds specified and then returns a numeric result which is the number of seconds actually delayed. You can specify any positive number including values less than 1, but the time resolution varies from system to system. It is usually around 10ms or better.

             [2]   .....
             [3]   'YOU HAVE 10 SECONDS IN WHICH TO WORK OUT THE ANSWER.'
             [4]   A←⎕DL 10
             [5]   'YOUR TIME IS UP.'