The correct answer is A -> ABxxbc. You have to try it inside a file, open it with vim and do :s/[ABC] [abc]/xx/

[root@centos7 ~]# echo "ABCabc" | sed "s/[ABC] [abc]/xx/" ABCabc [root@centos7 ~]# echo "ABCabc" | sed "s/[ABC][abc]/xx/" ABxxbc

tied on ubuntu output is ABCabc

There is a space between the brackets. Copied s/[ABC] [abc]/xx/ from the question into echo "ABCabc" | sed "" and outputs ABCabc.

The regular expression s/[ABC] [abc]/xx/ attempts to match a single character from the set [ABC] (i.e., A, B, or C), followed by a space, and then another single character from the set [abc] (i.e., a, b, or c). In the given string ABCabc, there is no occurrence where a space follows a character from the set [ABC]. Therefore, the regular expression doesn’t find any matches within the string, resulting in no changes to the original string. Hence, the output remains the same as the input string: ABCabc.

i've tried on terminal: right answer is A) ABxxbc

It's possible that you interpreted the regular expression as if it was being executed with single or double quotes, which could explain the discrepancy in the answer. In a context where the regular expression is executed with single or double quotes, the answer "A. ABxxbc" could be correct, as the regular expression "s/[ABC] [abc]/xx/" would look for an uppercase letter from "A" to "C", followed by a space, followed by a lowercase letter from "a" to "c", and replace it with "xx". However, in a context where single or double quotes are not required to execute the regular expression, the correct answer remains option "B. xxCxxc", as mentioned earlier. It's important to note that the execution of a regular expression can depend on the context and the parameters used, and there may be multiple correct answers.

in the question statement, it is not specified in what context the regular expression is being used, so it is assumed that it is used in a context where single or double quotes are not required. Therefore, the correct answer remains option "B. xxCxxc", as it is the result of applying the regular expression "s/[ABC] [abc]/xx/" to the string "ABCabc -"

The correct answer is A

the answer is a

Running the command echo "ABCabc" | sed "s/[ABC] [abc]/xx/" in Ubuntu 20.04 returns the result "ABCabc", so the correct answer is D.

[root@centos7 ~]# echo "ABCabc" | sed s/[ABC][abc]/xx/ <--- no space, no quotes ABxxbc [root@centos7 ~]# echo "ABCabc" | sed s/[ABC] [abc]/xx/ <--- with space, no quotes sed: -e expression #1, char 7: unterminated `s' command [root@centos7 ~]# echo "ABCabc" | sed "s/[ABC] [abc]/xx/" <--- with space, with quotes ABCabc So either A or D depending if there's a typo or not.

A for sure

Used with sed, retuns A

[root@centos7 ~]# echo "ABCabc" | sed "s/[ABC] [abc]/xx/" resultado com espaço "s/[ABC] [abc]/xx/" D = ABCabc

Definitely A, Tested and as per below comment on how to test it

A is correct