Step 1: Understanding clover leaf model.
The clover leaf model describes the secondary structure of transfer RNA (t-RNA), proposed by Robert Holley.
Step 2: Structure of t-RNA.
t-RNA folds into a characteristic clover leaf shape due to intramolecular base pairing.
Step 3: Elimination of other options.
DNA has a double helical structure.
m-RNA is linear and single stranded.
r-RNA forms complex ribosomal structures but not a clover leaf.
Step 4: Conclusion.
Hence, t-RNA shows the clover leaf model.