Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
When he was a little boy, Mark Twain would walk (A) along the piers, watch (B) the river boats, swimming (C) and fish in the (D) Mississippi, much like his famous character, Tom Sawyer
A. would walk
B. watch
C. swimming
D. the
C
“swimming” -> “swim”
“would + động từ nguyên thể”. Phía trước và phía sau đều dùng động từ nguyên thể: walk, watch, fish