X' and 'Y' agree to commit theft in 'Z's house but no theft is actually committed. They are guilty of-

Criminal conspiracy is committed when two or more persons agree to do an illegal act or a legal act by illegal means.

In this case, X and Y agreed to commit theft, which is clearly an illegal act under criminal law.

For the offence of criminal conspiracy, the agreement itself is sufficient; it is not necessary that the illegal act should actually be carried out.

Abetment by conspiracy requires some act or illegal omission in pursuance of the conspiracy, which is absent here.

There is also no instigation involved in the given facts.

Hence, even though no theft was committed, X and Y are guilty of criminal conspiracy, making Option B the correct answer.