Originally Posted by GrassLandings

No, not all 3 in my opinion. Think back to the definitions and reasons for either increasing or decreasing values of all 3 of those terms indiviually.

TAS increases with altitude, IAS decreases, AOA will likely need to increase due to the decrease in IAS.

Maybe the wording of the question is why people keep giving up different answers. I could see how one could read that, and assume the question is referring to the entire climb, level off, cruise process.
I see it as just "In a constant mach climb, what will you observe about TAS, IAS, and AOA as you climb to high altitude?"