How to find any element x of a set A, with three subsets B, C and D, by asking only three questions?

Question

The main set A = {s, w, p, n, l, d, c, b} has three subsets B, C and D.

B = {s, l, n, d}

C = {s, p, l, c}

D = {w, s, n, c}

Only three yes/no questions are required to find any element x. I don't understand how this is possible since the questions could vary depending on if the answer to a previous question is yes or no.

Answer 1

The three questions are:

1. Is $x$ in $B$?

2. Is $x$ in $C$?

3. Is $x$ in $D$?

If the answers are $\star\star\star$ the element is $\star$:

YYY, $s$

YYN, $l$

YNY, $n$

YNN, $d$

NYY, $c$

NYN, $p$

NNY, $w$

NNN, $b$