For two particles moving with constant velocities, let r⃗(t)=r⃗₀+v⃗_rt. Which statements are correct?

Select all that apply

• Option A

  At closest approach r⃗·v⃗_r=0

• Option B

  If r⃗₀·v⃗_r>0, they are initially moving apart

• Option C

  $t_min=-(r⃗₀·v⃗_r)/v_r²$ for unrestricted time

• Option D

  The perpendicular distance from origin to the relative-motion line equals |r⃗₀×v⃗_r|/|v⃗_r|