Q: You are presented with the quiz "What decreases when the density of an object increases?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity" and "an object is buoyant when it is less dense than the fluid around it". So, what's the best answer to the question?

Choose from:
[1]. support;
[2]. heat;
[3]. forces;
[4]. air cools;
[5]. heat energy;
[6]. buoyancy;
[7]. Pollution;
[8]. dry and hot;
A:
[6].