(a) A gas fills completely the vessel in which it is kept because the gas particles have negligible intermolecular forces, allowing them to move freely and randomly throughout the container, filling its entire volume.
(b) A gas exerts pressure on the walls of the container due to the constant random motion of gas particles which collide with the container walls, exerting a force on them.
(c) A wooden table should be called a solid because the particles in a solid are tightly packed together with strong intermolecular forces, giving it a definite shape and volume that cannot be easily compressed, unlike a gas.
(d) We can easily move our hand in air because air has very low density with particles far apart, allowing our hand to pass through easily, whereas a solid block of wood has tightly packed particles, requiring significant force to push through.