During a sideslip,
\[
\boxed{
\text{Bank with ailerons}
+
\text{Opposite rudder}
}
\]
is used to maintain runway alignment, especially during crosswind landings.
Step 1: Recall the sideslip maneuver.
A sideslip is a maneuver in which the aircraft is intentionally banked while applying opposite rudder to maintain the desired flight path.
Step 2: Identify the required control inputs.
During a sideslip,
\[
\boxed{
\text{Aileron is applied in one direction and rudder in the opposite direction.}
}
\]
This balances the aircraft and produces the desired sideways motion.
Therefore,
\[
\boxed{\text{Opposite aileron and rudder}}
\]
is the correct answer.
Thus,
\[
\boxed{(B)}
\]
is the correct answer.