Problem:
Mr. and Mrs. P are filing a joint return for the current year. They have two children. Marie, who is 18, earned $4,000 from a part-time job. James, who is 24 and attends college as a full-time student, earned $3,900 during the summer. Mr. and Mrs. P provide over one-half of their children's support. Mr. P's mother also lives with them but is self-supporting. How many exemptions can Mr. and Mrs. P claim on their current-year return?
A. 2
B. 3
C. 4
D. 5
Note: Be sure to show how you arrived at your answer.