We also had different students in some classes, so ______was a struggle to remember all the faces.

Does ______  matter if he can’t arrive here on time? 

Science is more than a collection of unrelated facts; to be meaningful and valuable, ______ must be arranged to show generalized character.

(2013·高考四川卷)The traffic on the main streets has a longer green signal than________on the small ones.

-How about his design?-Well, to tell the truth, it is______but satisfactory.