c. Linear (Ikkyo)

Ikkyo or first teaching is a fine example of moving to find the weakest base of support in uke. unbalancing through the toppling moment by lifting hands. stepping past uke and cutting down to complete the topple. the final pin too is an exercise in sensativity to pin uke without needing much force.

The figure below shows the footwork at the start of the kata, i leave the hand grab to your imagination

This figure shows the footwork to move to Omote position notice Nage's strong base aligned directly at Ukes weak base...excellent mechanical advantage...umm I mean Aiki here.

Driving through uke's arm  at an upward angle (yep its the topple angle), uke is now toppled onto their heels and completely compromised. Now can drive through and take them down onto the opposite shoulder, but thats not very aiki so ease up and allow their hips to move and finish with the pin.
Alternatively take them onto their toes, don't pull them down to do this as they will just step. instead take them up  at an angle - this is the topple angle remember.