7) E, B, A and C

i) E
A giant molecular structure would have a very high melting and boiling point. Also, it would not conduct electricity.

ii) B
A metal would have a moderate melting and high boiling temperature and would conduct electricity when solid or molten.

iii) A
An ionic compound would only conduct electricity when molten.

iv) C
Room temperature = 25º C.
The only substance that would be a liquid at room temperature would be the one which has a temperature lower than 25º C. This is only C.