C is obvious because no other choice has any closer answer
Because of the surface tention.
Explanation:
Part A
Boiling point of HF is much higher as compared to the boiling point of HCl.
Reason:
The strongest inter molecular hydrogen bonding exist between HF molecules This is due to highly electronegative Fluorine atom.
Part B
The type of bonding present in the given compounds are:
1. Ice
The water molecules in ice are linked to each other through intermolecular hydrogen bonding due to the presence of electronegative oxygen atom that is attached to hydrogen atom.
2. Copper dioxide
In Copper dioxide, Copper and oxide ions are linked to each other via electrostatic force of attraction due to the presence of electronegative Oxygen atom and electropositive Cu atom.
Therefore, ionic bond is present in it.
3. Steel
In steel, metal and negatively charged electrons are linked to each other, thus giving rise to metallic bond between steel molecules.
4. Silicon elastomer
In silicon elastomer, Silicon atom is linked to other atom via covalent bonds due to sharing of electrons.
5. Tungsten
In the case of tungsten also, atoms are bonded to each other via metallic bond.
