a. `overset(Θ)(O)H` can donate electron pair. Hence, it is a Lewis base
b. `F^(Θ)` can also donate electron pair. Hence, it is a Lewis base
c. `H^(o+)` can accept electron pair. Hence, it is a Lewis base.
d. `BCl_(3)` is deficient in electrons. Hence, it can aceept electron pair and is, therefore, a Lewis acid.