Concept: Plagiarism means using another person's work, ideas or words without proper acknowledgement. It is considered unethical in academic and research work.
Step 1: Check Assertion A.
Plagiarised work should be discouraged because it violates academic honesty and intellectual property rights.
\[
A = \text{Correct}
\]
Step 2: Check Reason R.
Reason R says that the boundary between plagiarism and research may sometimes be difficult because research builds on previous work. This is also a meaningful statement.
\[
R = \text{Correct}
\]
Step 3: Check explanation.
Reason R does not directly explain why plagiarised work should be discouraged. It explains the complexity of distinguishing plagiarism from legitimate use of previous work.
Therefore, both A and R are correct, but R is not the correct explanation of A.