A diverging lens of focal length `f_(1)` is placed in front of and coaxially with a concave mirror of foacl length `f_(2)`. Their separation is d. A parallel beam of light incident on the lens returns as a parallel beam from the arrangement. Then,
A. the beam diameters of the incident and reflected beams must be the same
B. `d=2|f_(2)|-|f_(1)|`
C. `d=|f_(2)|-|f_(1)|`
D. if the entire arrrangement is immersed in water, the conditions will remain unaltered
