∵−

1

2

≤x≤1，
∴x-1≤0，x-3<0，2x+1≥0，
∴

x2−2x+1

+

x2−6x+9

+

4x2+4x+1

=

(x−1)2

+

(x−3)2

+

(2x+1)2

=|x-1|+|x-3|+|2x+1|=1-x+3-x+2x+1=5．
故选B．