In which of the following methods of heat transfer is it necessary for the objects to be directly touching one another

What are the methods? Is this a multiple choice question?

Bis your answer to this

Which of the following is an example of an opposing signal? no examplthates given.   i would say, that traffic lights in a city at major intersections direct the flow of traffic in opposite directions so would be an example.also, stop signs on either side of the same street would be an example. at a train crossing, the light for allowing car traffic in opposite directions or not would be another example.