She treats the boy like that     she were his mother.

A．as if              B．even though       C．unless            D．although

The environment here has been greatly improved in recent years．    trees are thick and

 green，birds remain all the year long．

 A．Even if       B．Although          C．Unless            D．Where

_______there is enough food in the world for everybody, not everyone can afford to buy it.

A．Although                    B．Even if                C．Unless                 D．When

Tired _______ he was , he decided not to trouble her.