The verb in the example use is third-person, singular, present tense and so requires a final -s. For more information on subject-verb agreement, see Writing from A to Z (pages 184-188) or consult the LARC Electronic Writing Center Grammar Checklist.

Check the following resources for useful practice material: 1) Guide to Grammar and Writing, 2) Colleen Hildebrand's UCI Correction Symbols with hyperlinks.