Two students participated in a recruitment interview of a company together, and the person in charge of the company said to them, "We want to recruit three people from the interviewees, assuming that

Two students participated in a recruitment interview of a company together, and the person in charge of the company said to them, "We want to recruit three people from the interviewees, assuming that everyone participates in the interview." Suppose that X people (x≥3) participated in the recruitment interview of this unit.

Then the probability of two people being recruited at the same time is C 1x-2 C 3x = 1 70.

That is 6 (x-2) x (x-1) (x-2) =170,

That is x(x- 1)=420,

∴(x-2 1)(x+20)=0，

The solution is x = 2 1.

Therefore, choose: d.