For his Science project, Timor has 1 pea plant and 3 bean plants. He measures the heights of the plants once a week. This week's data are shown in the table. Which expression will help him find the average height of the bean plants this week?
A) (10 + 12 + 11 + 20) ÷ 4
B) (12 + 11 + 20) × 3
C) (12 + 11 + 20) – 3
D) (12 + 11 + 20) ÷ 3