Ans. D

The word ‘halcyon’ means ‘serene or calm’ and makes no sense here. The word ‘rattle’ means ‘to make upset or nervous’ and does not fit in the context. The correct word is ‘tradeoff’ which means ‘a balance achieved between two desirable but incompatible features; a compromise’. The word ‘compromises’ too makes sense here. Only option D can fit here.