using the law of conservation of energy
when two cars collide with each other then the momentum is same before collision and after collision but energy is changed after collision in form of heat and sound.
we know this collision is inelastic collision.
in inelastic collision, when two objects collide with each other then the momentum is conserved but kinetic energy is not conserved.
i) you walk barefoot on the hot street and it burns your toes.
the road is in direct contact with your skin. thermal energy from the road will transfer to the bottom of your feet, then to the rest of your body. this is an example of conduction.
ii) when you get into a car with hot black leather in the middle of the summer and your skin starts to get burned.
just like in the previous example, the hot leather is in direct contact with your skin (i guess if you're going to drive naked). thermal energy from the leather will transfe to your skin, then to the rest of your body. this is also conduction.
iii) a flame heats the air inside a hot air balloon and the balloon rises.
the flame heats air directly at the bottom of the balloon. the warm air expands and becomes less dense. this will rise and let the unheated, denser air in the balloon fall down toward the flame. this is an example of the convection cycle.
iv) a boy sits to the side of a campfire. he is 10 feet away, but still feels warm.
the campfire heats air directly nearby. the warm air expands and moves away from the fire in all directions, leaving behind unheated, denser air to be heated up. some of the warm air reaches the boy. this is another example of convection.
the answer is a) 1 and 2.
volleyball players can not touch the net while the ball is in play