What does the author mean by saying “but it’s one thing to improve a person’s ability to see words and quite another thing to improve his ability to read a text efficiently” in the second paragraph?（）
A.正确答案CThe ability to see words is not needed when an efficient reading is conducted.
B.The reading exercises mentioned can’t help to improve both the ability to see and to comprehend words.
C.The reading exercises mentioned can’t help to improve an efficient reading.
D.The reading exercises mentioned has done a great job to improve one’s ability to see words.
