Read the excerpt from Amy Tan’s essay “Mother Tongue.”

I know this for a fact, because when I was growing up, my mother’s “limited” English limited my perception of her. I was ashamed of her English. I believed that her English reflected the quality of what she had to say. That is, because she expressed them imperfectly her thoughts were imperfect.

Which phrase from the excerpt uses informal English?
A. “limited my perception”
B. “her English reflected the quality”
C. “she expressed them imperfectly”
D. “when I was growing up”