Correct statement

On moving down the group, melting point decreases because the atomic size of elements increases due to the addition of extra shell, the interatomic interactions becomes weak.

Melting point of Ga is the lowest melting point due to structural changes. Therefore, the given trend is correct.

Tin and lead will have lower melting points but lead, as an exception, has higher melting point than tin due to the distortion in tin's close-packed 12-coordinated structure. So, the correct order will be C>Si>Ge>Pb>Sn