All of us are_____aware of the cause of this failure, so do not make the same mistake again.

The incomes of skilled workers went up. ____, unskilled workers saw their earnings fall.

Nowadays, a lot of children have less time to play and communicate with their peer due to extra studies. ________, it is difficult to develop their character and social skills. 

 He put on his tie, took one last look at the room and_____________  walked out of the door.

It turned out that one of the children I thought a girl was _______ a boy.