A ball rolled into the ball suddenly. Explain the meanings of the two“balls" in this sentence. Which kind of sense relation do they belong to? Give the explanation of their origins.

Which of the following is NOT from back-formation?

Words created through back-formation are mostly

“Baby-sit”comes from “baby-sitter”by________

back-formation

Which two of the following are perfect homonyms?

Homophones are often employed to create puns for desired effects of________.

________is NOT a pair of homophones.

Vocabulary can refer to the total number of the words in a language, and it can stand for all the words used______, e.g. Old English vocabulary, Middle English vocabulary and Modern English vocabulary,

perfect homonyms