There are 2 correct answers I suppose, II and III.
Gas pressure is increased if the molecules inside the container hit the inner wall of the container faster (more frequently), or harder. These are 2 ways of how the gas pressure of some gas is increased. We can figure out if the options will increase the gas pressure.
For I, removing part of the gas, this will remove part of the gas molecules. In result, fewer molecules will hit the wall because some are removed, like the number density is reduced. This does not increase the gas pressure, but instead decreasing it. So, option I is not correct.
For II, if the container size is decreased, the gas molecules have a shorter distance to travel before they hit the inner wall of the container, so, they hit the wall faster and more frequently. This can help increase the gas pressure, so option II is correct.
For III, if the temperature of the molecules is increased, the molecules will have a higher kinetic energy. They tend to move faster and of course eventually, they hit the inner wall of the container more frequently. In addition, if they have a higher kinetic energy, they'll even hit the inner wall harder, which can increase the gas pressure too. Therefore, option III is correct too.
Find the density of the plastic. if the density is less than that of water, it's going to float. If it's more than the density of water, then it's going to sink.
