In New York City alone,six major institutions have spread up

In New York City alone,six major institutions(have spread up and out into the air space and neighborhoods around them) ___ (are preparing to do so)。括号内的两部分在成分上是并列的。意思为：六大主要研究所已经开始向外扩展并进入周围的空间以及邻区,(或者)正在准备这样做。所依据题意,只能选择or。