The Grammar of Vocabulary

For example WHO values/appreciates WHAT => i.e., what are the typical subjects and objects. This leads to CCQs.

What things can you spread?

What things can be spread?

What things can spread?

What is the missing word in this corpus extract generated by the Compleat Lexical Tutor.

How do we know?

What words do we know that are followed by as, can be used in the imperative,

In the corpus extract below, what are the subjects of the missing verb?