Don’t blame them any more-this is         because they are still young and lack experience.

If a student ____ in the exam, he won’t escape punishment.

If we leave right away，________ we’ll arrive on time.              

—Your sitting room looks so clean and tidy.—Well, thanks to the baby­sitter. She is a real ________.

Until the start of the Industrial Revolution, mankind was poor, hungry, and constantly at the _______ of disease and natural disasters.