Our teacher wasn’t blaming anyone ; he _______ said errors like this could be avoided．

After two years’ research, we now have a __________ better understanding of the disease. 

He began to take political science ________ only when he left school. 

The charity sale our school organizes every year has taught us much that we would never have _____ learned in class.

Bill always seems so self-confident, but _____ he’s extremely shy.