Answer:
Step-by-step explanation: 
 
for a.; 
 
Kinetic molecular theory assumes the collision of particles with each other and walls of container as perfectly elastic, that is why no particle loses energy. 
 
for b.; 
 
Kinetic molecular theory assumes that particles are of very small size incomparison with the size of container and far apart from each other that is why their density is very low. because density is described as 
 
Density = Mass/Volume 
 
So, one can imagine that in a big container, entire mass of all gas particles is very low as compared to the volume of container. So the gas have very low density 
 
For c.; 
 
Gases assume shape of their container because they are freely moving with in a container 
 
For d.; 
 
For statement in "b", one can easily understand that because according to kinetic molecular theory, particles are very small and at great distances, so they are compressible against any external pressure applied