The answer to this question relies on a clear understanding of the concept of 'pronouns' in parajumbles. The sentence mentions, 'this has meant a lot of uncertainty.... around... return to office...' It indicates that the preceding sentence discusses something related to the return to the office, and that particular element has caused a significant amount of uncertainty. Just before blank 2, there is a similar idea being presented: "The flow of workers back into offices has been more of a trickle than a steady stream, and this has meant a lot of uncertainty around what a wide-scale return to the office might look like in practice..."