This question raises once again the thorny topic of multiple answers – which I last wrote about, I believe, in Week 8 of last season.
As anyone who's ever played in this or any other quiz league should be aware, if a question has more than one answer there's a risk that the first team that the question is addressed to gets one half right and the other half wrong; if the other team knew the answer that the first team got wrong but not the one they got right, they now have both answers – thus giving them an unfair advantage.
The fact that this is "only a supplementary" is no excuse. As I've also said before, supplementaries are only used when something has gone wrong, so there's already likely to be tension. Like Caesar's wife, they need to be above suspicion.
It's almost always possible to rewrite a question so that it has only one answer. You can often do it by asking the question the other way round: "At which US location did Egypt and Israel sign a peace agreement in 1978?"
© Macclesfield Quiz League 2018