[单选题]
A 2.0-kg mass is attached to the end of a horizuwboo .p6z7 u8ontal spring of wnwl;9l(:v 9e+lr ; -nbvakbcspring constant 50 N/m and s;e+:llv9cnk- wnvb ;rwl9 ab(et into simple harmonic motion with an amplitude of 0.10 m. What is the total mechanical energy of this system?
A. $0.020 \; J$
B. $25 \; J$
C. $0.25 \; J$
D. $1.0 \; J$