The correct option is
D Policy of achieving ends by slow and constitutional methods
Option A is the correct answer because 'a Fabian policy' refers to a policy of delays and cautions. The origin of the phrase is relating to, or in the manner of the Roman general Quintus Fabius Maximus who is known for his defeat of Hannibal in the Second Punic War by the avoidance of decisive contests.
Options B, C, D and E are incorrect because these are not the meanings of the give phrase as has been explained above.