Answer
$CH_3CH_2CH_2CH_2$, SiC
Work Step by Step
From the list, we see that $CH_3CH_2CH_2CH_2$ contains covalent bonding with only the london dispersion force. Thus, it has the lowest melting point. SiC contains a network of covalent bonds. Like substances such as diamond, this corresponds to an extremely high melting point.