The output of the program date should be saved in the variable actdat. What is the correct statement?

Wrapping date in backticks performs command substitution, executing the date command and assigning its stdout output to actdat. This is the classic POSIX-compatible syntax; the modern equivalent is actdat=$(date). Both forms replace the expression with the command's output before the assignment occurs.

The set builtin modifies shell options or positional parameters, not named variable assignments; set actdat=`date` is invalid syntax for variable assignment.

The > operator redirects output to a file; date > $actdat would write to a file whose name is the current value of actdat, not store date's output in the variable.

$(actdat) is command substitution that attempts to execute actdat as a command, not a redirection of date's output into a variable.

actdat=date assigns the literal string 'date' to the variable rather than the output of running the date program.