How did the author introduce the topic of this passage?
A、By describing grammar errors made by kids.
B、By sharing experiences of speech therapists.
C、By using Tom' s case as an example.
D、By stating his personal views to readers.
Directions:In each of the following groups of words, there are four underlined letters or ltter combinations marked A, B, C and D. Compare the underlined parts and identify the one that is different from the others in pronunciation. Mark your answer by blackening the corresponding letter on the Answer Sheet.