It seems reasonable to assume that ,other things _____(be) e

It seems reasonable to assume that ,other things _____(be) equal,they would~~~为什么那么添
It seems reasonable to assume that ,other things _____(be) equal,they would prefer single to shared rooms.

eing
意思为：其他条件相同的情况下,他们宁愿单住,也不愿意共用房间,这个假设是有道理的.
other things being equal（其他条件相同的情况下）是一个独立主格结构,即意义上具有“主位关系”的结构,但不是严格意义上的语法上的“主谓”,所以动词只能用非谓语形式（不定式、分词等）或者其他结构（如介词短语等）.
独立主格结构在句中常作状语,相当于一个状语从句.
比如本句中相当于if/when/as long as other things are equal.
本句主干就是：It seems reasonable to assume + that 从句