The differences between mRNA amd tRNA are that
mRNA has more elaborated 3-dimensional structure due to extensive base -pairing
(ii) tRNA has more elaborated 3-dimensional structure due to extensive base -pairing
(iii) tRNA is usually smaller than mRNa
(iv) mRNA bears anticodon but tRNA has codons.

Options

A. (i)and (ii)
B. (ii) and (iii)
C. (i),(ii) and (iii)
D. (i),(ii),(iii) and (iv)

Answer

To solve the question regarding the differences between mRNA and tRNA, we will analyze each statement provided and determine its accuracy.

### Step-by-step Solution:

1. **Statement Analysis**:
- **Statement (i)**: "mRNA has more elaborated 3-dimensional structure due to extensive base-pairing."
- **Analysis**: This statement is incorrect. mRNA does not have a highly elaborate 3D structure due to extensive base pairing. It is primarily linear and does not fold extensively like tRNA.

- **Statement (ii)**: "tRNA has more elaborated 3-dimensional structure due to extensive base-pairing."
- **Analysis**: This statement is correct. tRNA has a complex three-dimensional structure, often described as a cloverleaf or leaf-like shape, due to extensive base pairing within the molecule.

- **Statement (iii)**: "tRNA is usually smaller than mRNA."
- **Analysis**: This statement is also correct. tRNA molecules are generally much smaller than mRNA molecules, which can be quite long and encode for many amino acids.

- **Statement (iv)**: "mRNA bears anticodon but tRNA has codons."
- **Analysis**: This statement is incorrect. mRNA contains codons, which are sequences of three nucleotides that specify amino acids. tRNA, on the other hand, has anticodons, which are complementary to the codons on mRNA.

2. **Conclusion**:
- Based on the analysis, the correct differences between mRNA and tRNA are:
- (ii) tRNA has a more elaborated 3-dimensional structure due to extensive base-pairing.
- (iii) tRNA is usually smaller than mRNA.
- Therefore, the correct answer is that only statements (ii) and (iii) are correct.

### Final Answer:
The correct differences between mRNA and tRNA are:
- tRNA has a more elaborated 3-dimensional structure due to extensive base-pairing.
- tRNA is usually smaller than mRNA.