单项选择题
A．but B．yet C．and D．so
A．workers often got ill because of the poor working conditions B．companies were free to put out any products they wanted to C．many people were killed by dangerous products D．industries were as careful in management as they are today
A．building the proper knowledge and habits in human beings B．safeguarding the forests from fire C．posting rules in forests D．holding the damage to a minimum