NEET Class neet Answered

The melting temperature depends on both the length of the molecule and the specific nucleotide sequence composition of that molecule. The guanine-cytosine pair is bound by three hydrogen bonds, while adenine-thymine pairs are bound by two hydrogen bonds. DNA with high GC content is more stable than DNA with low GC content. 

Generally, DNA rich in A:T does have a low melting temperature. Thus, for example, in very long DNA molecules with stretches rich in A:T pairs, and other regions rich in G:C pairs, the A:T stretches will melt before the G:C ones when the temperature is gradually increased. 

From the given options, option B contains the maximum A:T bondings. Hence, it will melt at the lowest temperature.