According to some estimates, at most for how long can we use the fossil fuel reserves

A．international cooperation via the Internet
B．how dangerous thallium can be to humans
C．how one can get help from the Internet
D．the girl’s recovery from thallium poisoning

A．the different objectives of those involved in these respective pursuits
B．the different methods they employ in the collection of data to support their theories
C．the different ways in which they attempt to extend accepted conventional forms
D．the different principles of organization that they utilize in order to create new works