This document discusses common problems with verbs, nouns, pronouns, and other parts of speech on the TOEFL exam. It provides examples of incorrect and correct usage of tenses, singular/plural forms, countable/uncountable nouns, irregular plurals, and subject/object pronouns. The document then practices each concept by presenting example sentences for students to identify as correctly or incorrectly using the target grammar points. The goal is to help students recognize and avoid frequent grammatical errors in order to improve their performance on the TOEFL written expression section.