Functionality means characteristics related with achievement of purpose.

So, (a) $\rightarrow$ (ii)

Reliability means capability of software to maintain its performance.

So, (b) $\rightarrow$ (iv)

Efficiency means relationship between level of performance and amount of resources used.

So, (c) $\rightarrow$ (i)

Maintainability means efforts needed to make improvement.

So, (d) $\rightarrow$ (iii)

Hence, correct matching is:

(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)