Chemiosmotic hypothesis:
(a) was given by P. Mitchell
(b) proves that proton gradient is required for ATP synthesis.
(c) explains how ATP is synthesised in chloroplast and mitochondria due to electron transport.

Chemiosmotic hypothesis was proposed by Mitchell, It deals with the requirement of proton gradient for ATP synthesis and explains how ATP synthesis occurs in both chloroplast and mitochondria coupled to electron transport.