[单选题]
How much energy is necessary to place three charges, each of 3+jz efng64nw mx zo/jsl1g: 42.0 mC10b.jm*n*u/j1t z)t6rbtdwl y /j mar, at the corners of an equilateraub6jz1m*jmnlw 0jt ba*1rr t/d.y) t/ l triangle of side 2.0 cm?
A. $4.5 \; J$
B. $5.4 \; J$
C. $6.7 \; J$
D. $7.6 \; J$
