Which of the following is correct [DPMT 1997]

• A. Crystal systemAxial distanceAxial anglesExamplesCubic\[a\ne ~b=c\]\[\alpha =\beta \ne \gamma =90{}^\circ \]\[Cu,\text{ }KCl\]
• B. Crystal systemAxial distanceAxial anglesExamplesMonoclinic\[a\ne ~b=c\]\[\alpha =\beta =\gamma =90{}^\circ \]\[PbCr{{O}_{2}},PbCr{{O}_{4}}\]
• C. Crystal systemAxial distanceAxial anglesExamplesRhombohedral\[a=~b=c\]\[\alpha =\beta =\gamma \ne 90{}^\circ \]\[CaC{{O}_{3}},\text{ }HgS\]
• D. Crystal systemAxial distanceAxial anglesExamplesTriclinic\[a=~b=c\]\[\alpha \ne \beta =\gamma \ne 90{}^\circ \]\[{{K}_{2}}C{{r}_{2}}{{O}_{7}},\text{ }CuS{{O}_{4}}.\text{ }5{{H}_{2}}O\]