It’s difficult to ___ these old books for some of them ______ none of the classification.

Modern science and technology has __________ communication between people far apart.

Knowledge and learning are important if we want to be successful, but they may also ______ our thinking.

When you meet a new word in reading the English papers, you can guess its meaning but needn’t always ______ the dictionary.

After he lost his job, he _____ debt and eventually paid it off.