The approximate \( Z_{\text{eff}} \) felt by a valence electron of boron and oxygen are:
\[
\boxed{Z_{\text{eff}} \text{ for Boron} = 2.6}
\]
\[
\boxed{Z_{\text{eff}} \text{ for Oxygen} = 4.55}
\]
Given the multiple-choice options, the closest match is:
\[
\boxed{+3 \text{ and } +6}
\]