A system that changes spontaneously without an enthalpy change select one:

a. is impossible.

b. becomes more disordered.

c. becomes more ordered.

d. releases heat.

I believe a system that changes spontaneously without an enthalpy change becomes more disordered. Spontaneous reactions are driven by decreasing enthalpy and increasing enthalpy. A sponataneous reaction occurs without being driven by some outside force. Chemical reacrions are driven by two driving forces, namely, the enthalpy and the entropy.