[单选题]
A 10-kg mass, hung onto a spring, causes the spring to bnhh.7zf7y 4e3l7 itxzz)xe( 9u)ed- jqt u6o*ozyq3 stretch 2.0 cm. What is the springutozqyequ 9j3d - *o6) constant?
A. $4.9 \times 10^{3} \; N/m$
B. $5.0 \times 10^{3} \; N/m$
C. 20 N/m
D. 2.0 N/m
