What do you think.
For me the answer is none of the above, because if you heat enough you can break the atoms beyond that, but that’s just me and I don’t ask anyone to do my homework on the net. So prove you work, share your doubts and you will find help, post your question and hope for a free lunch, and you will get sarcasm.

When a protein is denaturated by heating, it loses the structures in this sequence: quaternary–>tertiary—>secondary—>primary. So answer is b)hydrogen ( secondary structure; primary structure is supported by covalent bonds).

I agree with MisterATP for the most part, but the answer has to be disulfide bonds.

Ionic interactions are the 1st to go, hydrogen and hydrophobic both support secondary structure, disulfide bonds are covalent and not easily destroyed by heat (if they are affected at all).

Yes, I think my answer isn’t right. I have forgotten one thing: hydrogen bonds are in quaternary structure yet! So it isn’t a need to go on secondary structure as I wrote.

The quaternary structure is supported by ionic, disulphide, van der Valse and hydrogen bonds. But hydrophobic bonds appear just in tertiary structure. So according to sequence I wrote, answer would be c) hydrophobic interactions.

To clarify:

you are correct in your order, but disulfide bonds are exception to the ‘rule’. They are covalent bonds and would break out of order.

Cat is right.

@Candice: the best to approach this question is from a chemistry perspective: look up each type of bond in a chemistry book or on the internet and you will discover that disulfide bonds, being covalent, are the hardest, and therefore last to break. But that is a bit harder than asking for the answer