Consider a linear diversity combining receiver operating in a Rayleigh fading environment with M independent and identically distributed (iid) diversity branches.

(a) Which type(s) of diversity (space, frequency, time, polarization, and multipath)
(i) cannot accommodate 5-order diversity
(ii) is difficult to implement in a mobile handset
(iii) requires very wide transmission bandwidth
(iv) these two can be used together