[单选题]
A mass of 50 kg is suspended from a r9z:i1 tums)k steel wire of diameterdz9kix.(9em : ru.hsv 1.0 mm and length 11.2 m. How much will the wire stretch? The Young's modulus for d hvsru:mze.i9k9 .(x steel is $20 \times 10^{10} \; N/m^2$.
A. $1.5 \; cm$
B. $2.5 \; cm$
C. $3.5 \; cm$
D. $4.5 \; cm$
