Why do experts use one kind of explosive for steel columns and another for concrete columns

I think it’s the first option.

The second option isn’t true because the fabric protects people from the debris, it doesn’t actually explode the concrete

The third option isn’t true because steel and concrete need different explosives, not necessarily “more” If anything I think concrete needs more explosives because steel needs to be broken in one place

The last option could be true but I didn’t read anything about putting steel explosives in holes

It would have to be c or d

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.