Pair-list readings of conjoined singular which-phrases

The following generalization seems to hold: conjoined singular which-phrases have PL readings only if the predicate is collective: collective predicates like live together, like each other, are married, etc. give rise to PL readings, while distributive predicates like are European, like math, etc. do not. We further note that not all collective predicates give rise to the PL reading; the predicate to be tennis partners does not as readily allow a PL reading when compared with (2a). It is not clear at this moment what differentiates the two classes of collective predicates as the distinction does not seem to align with Winter’s (2001, 2002) distinction between ‘set’ and ‘atom’ predicates.