Ms Zhang was a baby-sitter in a German family living in China. She got on well with the whole family at the beginning though her English was very limited. Ms. Zhang was a good cook and the whole family was very pleased with her delicious food. However, before the dinner, she always said to them: “I am sorry that I am a poor cook. Please try the dishes cooked by me. If they are bad, please forgive my fault.” The German couple was surprised to hear what she said for the first time, because the dishes were unexpectedly very delicious. However, she repeated it as a rule whenever she put the dishes on the table. The couple’s confusion finally led to the belief that Ms. Zhang was hollow-hearted. They could not understand why she was lying. Could you explain to the German couple why Ms. Zhang said she was a poor cook when she was actually a good one?