I'll give you a question, please answer with step-by-step reasoning process.
He was trying to buy a new mattress, he wanted something soft yet what?\nOptions:\n- hexachord\n- loud\n- hard\n- harsh\n- firm

firm
A new mattress should be firm as well as soft.

As he was trying to buy a new mattress so he wanted it to be soft yet firm.

.

Thus, the answer is firm