The following list of statements is given:

• A. Grashoff’s rule states that for a planar crank-rocker 4-bar mechanism, the sum of the shortest and longest link lengths cannot be less than the sum of the remaining two link lengths.
• B. Inversions of a mechanism are created by fixing different links, one at a time.
• C. Geneva mechanism is an intermittent motion device.
• D. Grubler’s criterion assumes mobility of a planar mechanism to be one.