  Assume $\text{MA}(\kappa)$. We show that for every real chain of size
$\kappa$ in the quotient Boolean algebra $P(\omega)/fin$ we can find an almost
chain of representatives such that every $n\in\omega$ oscillates at most three
times along the almost chain. This is used to show that for every countable
discrete extension of a separable compact line $K$ of weight $\kappa$ there
exists an extension operator $E:C(K)\longrightarrow C(L)$ of norm at most
three.
