Official Explanation
Read the Original Sentence Carefully, Looking for Errors:
The sentence as written contains no errors. The underlined portion consists of just nouns, which are part of a parallel construction. The sentence describes a new invention that can be used "to calculate the pressure ... and to detect the starting and ending points ...." Note that the two parts of this construction are parallel in form. Expect to choose (A), but check the other choices to make sure nothing
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Read the Original Sentence Carefully, Looking for Errors:
The sentence as written contains no errors. The underlined portion consists of just nouns, which are part of a parallel construction. The sentence describes a new invention that can be used "to calculate the pressure ... and to detect the starting and ending points ...." Note that the two parts of this construction are parallel in form. Expect to choose (A), but check the other choices to make sure nothing
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