Re: F-35b
The last version considered for the chop was the A (CTOL). Sea-based airpower is considered A Good Thing these days; the Marines usually get what they want; the USAF has half-endorsed STOVL; and there are those who would like to target the C (CV) but they are not ready yet, and don't really need to be.
The A was spared apparently because cancelling it would not save very much money. Reason - the basic structure, landing gear and up-and-away aero are the same as the B, while the propulsion system and weapon bays are the same as the C. Also, most of the early flight-test aircraft are As and it's too late to change that.