Final answer:
The two-dimensional structure of tRNAs is represented by a cloverleaf shape.
Step-by-step explanation:
The answer to the question is option b: cloverleaf.
tRNA molecules have a two-dimensional structure, which is commonly referred to as a cloverleaf structure. This structure is formed by intramolecular base pairing, resulting in loops and double-stranded portions. The cloverleaf shape consists of four arms: the amino acyl arm, anticodon arm, dihydrouridine arm, and ribothymidine-pseudouridine arm.