For a science experiment, Matt places a flashlight on the table on the east side of a potted plant. He covers the plant and flashlight with a darkened box. Matt waits several days, then checks to see how the plant is growing. Which of the following results is an example of phototropism? 

a- The plant grows toward the south.

b- The plant grows toward the west.

c- The plant grows toward the east.

d- The plant continues to grow upward.