My teacher says if they were that they would still be standing today. I'm not sure if he means the reinforced steel in the concrete beams, columns etc or if the whole beams and columns floor etc were were made of reinforced steel.
There is no way you could make a 110 floor building out of concrete.
Reinforced Steel is found in concrete, and if the towers were built with reinforced concrete (concrete beams with rebar) then they would likely still be standing. The twin towers were made of steel. When steel is heated up, it deforms and collapses, which is why it didnt stand up. One of the top 2 things against steel is that it is not fire resistant.
