What condition of the gas remains constant?

The temperature remains constant because the internal energy only depends on temperature in that case

-Hops

b. atoms in metallic solids are not arranged in a regular pattern

explanation:

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.