A lense of focal length f is placed in between an object and screen at a distance D. The lens forms two real images of object on the screen for two of its different positions, a distance x apart. The two real images have magnification `m_1 and m_2` respectively `(m_1gtm_2).` Choose the correct statement(s).
A. `m_1m_2=-1`
B. `m_1m_2=1`
C. `f=(D^2-x^2)/(4D)`
D. `Dge4f`