阅读材料，回答下面5个问题。 touch命令用来更新指定文件上的时间戳。使用以下用法信息和touch命令的调用示例回答后面8个问题。 [madonna @station madonna]$ which touch /bin/touch [madonna@station madonna]$touch –help Usage: touch [OPTION]…FILE… Update the access and modification times of each FILE to the current time. Mandatory arguments to long options are mandatory for short options too. -a change only the access time -B SEC, --backward=SEC date back SEC seconds -c, --no-create do not create any files -d, --date=STRING parse STRING and use it instead of current time -F SEC, --forward=SEC date forward SEC seconds -f (ignored) -m change only the modification time -r, --reference=FILE use this file’s times instead of current time -t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time --time=WORD set timer given by WORD:access atime use (same as -a) modify mtime (same as -m) --help display this help and exit --version output version information and exit [madonna@station madonna]$touch –r /etc/services touch: file arguments missing Try ‘touch --help’ for more information. [madonna@station madonna]$tooch /etc/services -bash: tooch: command not found [madonna@station madonna]$touch –k /etc/services touch:invalid option –k Try ‘touch --help’ for more information [madonna@station madonna]$touch –r /etc/services /tmp/foo 以下哪一项是对touch命令的合法调用？ A: touch –k /etc/services B: touch –ac /etc/services C: touch –nocreate /etc/services D: touch –t