a) Structure should be aesthetically pleasing but structurally unsafe

b) Structure should be cheap in cost even though it may be structurally unsafe

c) Structure should be structurally safe but less durable
d) Structure should be adequately safe, should have adequate serviceability

Answer: d
Explanation: Structure should be designed such that it fulfils it intended purpose during its lifetime and be adequately safe in terms of strength, stability and structural integrity and have adequate serviceability. Structure should also be economically viable, aesthetically pleasing and environment friendly.