In the midst of utter devastation and chaos, a father left his wife safely at home and rushed to the school where his son was supposed to be, only ________ that the building was as flat as a pancake．

A．to discover

B．to be discovered

C．discovering

D．discovered

where＆what选词填空。

In the midst of utter devastation and chaos, a father left his wife safely at home and rushed to the school ________ his son was supposed to be, only to discover that the building was as flat as a pancake．