A file called testfile has both uppercase and lowercase letters: $ cat testfile ABCDEfgH IJKLmnoPQ abcdefgH ijklLMNopq A Linux administrator is…

The tr (translate) utility reads characters from standard input and replaces or deletes them before writing the results to standard output. To convert lowercase ASCII characters to uppercase, tr requires the source character set [a-z] as its first argument and the target replacement set [A-Z] as its second argument. The syntax tr '[a-z]' '[A-Z]' properly specifies this translation mapping. Redirection operators (such as outputfile) direct standard input from testfile and standard output to uppercase. Among the provided choices, option D specifies the correct tr command syntax and character range order required to perform lowercase-to-uppercase translation across all text input.

A. tr '(A-Z}' '{a-z}' uppercase: Uses incorrect character ranges and reverses translation order, mapping uppercase characters into lowercase instead of converting lowercase to uppercase.
B. echo testfile | tr "[Z-A]" "[z-a]" uppercase: Passes only the string literal "testfile" rather than file contents, and specifies invalid reverse character ranges [Z-A] and [z-a].
C. cat testfile | tr '{z-a)' '{Z-A}' uppercase: Uses invalid reverse character ranges (z-a) and improper brace syntax, which prevents valid character translation by tr.

GNU Coreutils Manual: Section 11.2 tr: Translate characters. https://www.gnu.org/software/coreutils/manual/html_node/tr-invocation.html

IEEE Std 1003.1-2017 (POSIX.1): tr utility specification. https://pubs.opengroup.org/onlinepubs/9699919799/utilities/tr.html