In DNA A corresponds to T and C corresponds to G, the only difference in RNA is that T is replaced with U, so the mRNA sequence that corresponds to the codon AGT would be UCA.
That is the coding sequence, noncoding DNA sequences can in some instances produce tRNA and rRNA but they never code for mRNA so a noncoding sequence of DNA would not have a corresponding mRNA sequence.
It may be possible that I am misreading the question however, as I found it oddly worded.
The reason there can be only two answers and the reason non-coding DNA doesn't produce mRNA is because coding DNA refers to DNA that codes for proteins, since mRNA is the go between for DNA and the ribosomes for protein synthesis non-coding DNA will not produce mRNA by definition. Since there is only the two types of DNA possible in this problem there is actually only two questions not three.