Consider the following statements pertaining to heat transfer through fins

$($i$)$ They must be arranged at right angles to the direction of flow of working fluid

$($ii$)$ The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements

$($iii$)$ Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid

$($iv$)$ Fins are made of materials that have thermal conductivity higher than that of wall

Identify the correct statements

a$)$ i and ii

b$)$ iii and iv

c$)$ i and iv

d$)$ ii and iii