The answer you are looking for is A. "Cylinders shall be moved by tilting and rolling them on their bottom edges".
The reason this is not a proper way to transport gas cylinders, is because rolling and tilting them in such a manner could lead to dents in the container, which builds up the pressure inside the container and could lead to leakage of the gas from the inside to the container to the outside. Thus meaning A is the answer.
I hope this helps!