Let y = x/e x.

y'=( 1-x)e^(-x)

X∈(-∞, 1), y'>0, on which the function simply increases, and the range (-∞, 1/e).

X∈( 1, +∞), y'<0, where the function is a simple subtraction with the range of (0, 1/e).

X= 1, y'=0, and the maximum value of the function at x= 1/e.

When x=0, y=0.

(you can make a general picture of y = x/e x from the above)

The previously known equation is: y+ 1/(y- 1)+m=0, that is, y? +(m- 1)y-(m- 1)=0

It is known that the equation must have two real roots y 1, y2 and y 1

Root x 1 (x 1

Roots x2, x3 (0

de(x 1/e x 1)- 1 = y 1- 1，(x2/e x2)- 1 =(x3/e x3)- 1。

Let u=y- 1, then y=u+ 1.

Equation y? +(m- 1)y-(m- 1)=0%: u? +(m+ 1)u+ 1=0

U 1 = Y 1- 1 and U2 = Y2- 1 are its two roots.

u 1 u2= 1

Evaluation formula =(y 1- 1)? (y2- 1)？

=(u 1 u2)？ = 1

So choose B.