I agree with A & C, but I would like to go one further.
If one gear (main) will not extend, first of all go to an airfield with "proper" emergency services. Then if grass land gear up (all up), if tarmac land with remaining gear down. If the wing digs in on grass, ouch!
Personally if I am landing on grass with failed gear of any sort, I would land gear up everytime. The Arrow I fly often had a gear up landing by mistake, no damage except for prop. The Piper has runners underneath just for that mistake.
I have had several gear probs on Arrows and Senaca's (same gear system). One thing I would say is don't do the emergency free fall until you have tried other avenues and had the gear inspected by a fly-by.
One time all my gear stuck half way. My concern was if I tried free fall - A) it was stuck; B) free fall works best from starting fall when fully up. Therefore if motor will get gear back up do that before doing free fall. As it happenened motor was worn out.