(a) `OH^(-)` can donate electron pair. Hence, it is a Lewis base
(b) `F^(-)` can also donate electron pair. Hence, it is a Lewis base
(c) `H^(+)` can accept electron pair. Hence, it is a Lewis acid
(d) `BCl_(3)` is deficient is electrons. Hence, it can accept electron pair and is, therefore, a Lewis acid.