The correct option is B All of the above
The primary structure of tRNA is a small, linear, single-stranded nucleic acid. This tRNA due to its stretches of complementary base pairs forms two-dimensional secondary structure, which is in the form of a cloverleaf. Modifications to form the stem-loop and anticodon loop are important for tRNA stability and functioning. Thus it undergoes post-translational changes. Thus the correct answer is option D.