One of the errors that the HSPT will ask you to catch is whether the subject of a sentence agrees with the verb in a sentence. This sounds simple enough, but sometimes we cannot count on an easy sentence that just "sounds wrong" when we read it.
To catch these errors on the test, you need to be aware of what the verb is in the sentence and its number, and you also have to be able to identify the verb and its number. Watch the video below for a process that you can apply to check a sentence for subject-verb agreement.