_________ I picked up the receiver, I realized that someone had dialed the wrong number.

(2013·安徽名校联考Ⅱ)________ nearly all behavior is learned behavior is a basic assumption ________ has been put forward by social scientists.

Russia’s cutting off the gas supply raised a major concern to the European Union, ______ a number of member states are increasingly dependent on one single supplier.

Wang Pin is an orphan.He has no dad ___ mum.

 It is difficult for us to learn a lesson in life ______ we’ve actually had that lesson.