Answer
b) $Li_2O$
d) $CaO$
Work Step by Step
b) and d) are the only basic anhydrides, since a base can be obtained by their reaction with water:
b) $Li_2O+H_2O\rightarrow 2LiOH$
d) $CaO+H_2O\rightarrow Ca(OH)_2$
In every other case, an oxide would react with water to afford an acid.
