He pointed out that a (considerable) gap (existing) between the number of hours people (are paid) for working and the number of hours (spent) in productive labor.

单项选择题We are (at) a critical point in our nation's history and we cannot go back as individuals or (as a country) to (what) .we were ten, five or even one year (earlier).

单项选择题Scientists created a (brainy), four-legged robot (resemble) a starfish that can sense (damage) to its body, and (think up) a way to recover.