JEE Advanced 2007 Physics question

A student performs an experiment to determine the Young's modulus of a wire, exactly 2 m long, by Searle's method. In a particular reading, the student measures the extension in the length of the wire to be 0.8 mm with an uncertainty of ±0.05 mm at a load of exactly 1.0 kg. The student also measures the diameter of the wire to be 0.4 mm with an uncertainty of ±0.01 mm. Take g = 9.8 m/s² (exact). The Young's modulus obtained from the reading is

• (A) N/m² (this is also correct)
• (B) N/m²Correct
• (C) N/m²
• (D) N/m²